diff --git a/cc/ccdeps.go b/cc/ccdeps.go
index d30abba..469fe31 100644
--- a/cc/ccdeps.go
+++ b/cc/ccdeps.go
@@ -85,9 +85,8 @@
 	moduleDeps := ccDeps{}
 	moduleInfos := map[string]ccIdeInfo{}
 
-	// Track which projects have already had CMakeLists.txt generated to keep the first
-	// variant for each project.
-	seenProjects := map[string]bool{}
+	// Track if best variant (device arch match) has been found.
+	bestVariantFound := map[string]bool{}
 
 	pathToCC, _ := evalVariable(ctx, "${config.ClangBin}/")
 	moduleDeps.C_clang = fmt.Sprintf("%s%s", buildCMakePath(pathToCC), cClang)
@@ -96,7 +95,7 @@
 	ctx.VisitAllModules(func(module android.Module) {
 		if ccModule, ok := module.(*Module); ok {
 			if compiledModule, ok := ccModule.compiler.(CompiledInterface); ok {
-				generateCLionProjectData(ctx, compiledModule, ccModule, seenProjects, moduleInfos)
+				generateCLionProjectData(ctx, compiledModule, ccModule, bestVariantFound, moduleInfos)
 			}
 		}
 	})
@@ -180,26 +179,30 @@
 }
 
 func generateCLionProjectData(ctx android.SingletonContext, compiledModule CompiledInterface,
-	ccModule *Module, seenProjects map[string]bool, moduleInfos map[string]ccIdeInfo) {
+	ccModule *Module, bestVariantFound map[string]bool, moduleInfos map[string]ccIdeInfo) {
+	moduleName := ccModule.ModuleBase.Name()
 	srcs := compiledModule.Srcs()
+
+	// Skip if best variant has already been found.
+	if bestVariantFound[moduleName] {
+		return
+	}
+
+	// Skip if sources are empty.
 	if len(srcs) == 0 {
 		return
 	}
 
-	// Only keep the DeviceArch variant module.
-	if ctx.DeviceConfig().DeviceArch() != ccModule.ModuleBase.Arch().ArchType.Name {
+	// Check if device arch matches, in which case this is the best variant and takes precedence.
+	if ccModule.Device() && ccModule.ModuleBase.Arch().ArchType.Name == ctx.DeviceConfig().DeviceArch() {
+		bestVariantFound[moduleName] = true
+	} else if _, ok := moduleInfos[moduleName]; ok {
+		// Skip because this isn't the best variant and a previous one has already been added.
+		// Heuristically, ones that appear first are likely to be more relevant.
 		return
 	}
 
-	clionProjectLocation := getCMakeListsForModule(ccModule, ctx)
-	if seenProjects[clionProjectLocation] {
-		return
-	}
-
-	seenProjects[clionProjectLocation] = true
-
-	name := ccModule.ModuleBase.Name()
-	dpInfo := moduleInfos[name]
+	dpInfo := ccIdeInfo{}
 
 	dpInfo.Path = append(dpInfo.Path, path.Dir(ctx.BlueprintFile(ccModule)))
 	dpInfo.Srcs = append(dpInfo.Srcs, srcs.Strings()...)
@@ -216,9 +219,9 @@
 	dpInfo.Local_Cpp_flags = parseCompilerCCParameters(ctx, ccModule.flags.Local.CppFlags)
 	dpInfo.System_include_flags = parseCompilerCCParameters(ctx, ccModule.flags.SystemIncludeFlags)
 
-	dpInfo.Module_name = name
+	dpInfo.Module_name = moduleName
 
-	moduleInfos[name] = dpInfo
+	moduleInfos[moduleName] = dpInfo
 }
 
 type Deal struct {
diff --git a/cmd/release_config/release_config_lib/release_configs.go b/cmd/release_config/release_config_lib/release_configs.go
index f2e1388..a4c884c 100644
--- a/cmd/release_config/release_config_lib/release_configs.go
+++ b/cmd/release_config/release_config_lib/release_configs.go
@@ -42,6 +42,10 @@
 
 	// Flags declared this directory's flag_declarations/*.textproto
 	FlagDeclarations []rc_proto.FlagDeclaration
+
+	// Potential aconfig and build flag contributions in this map directory.
+	// This is used to detect errors.
+	FlagValueDirs map[string][]string
 }
 
 type ReleaseConfigDirMap map[string]int
@@ -317,6 +321,21 @@
 		return err
 	}
 
+	subDirs := func(subdir string) (ret []string) {
+		if flagVersions, err := os.ReadDir(filepath.Join(dir, subdir)); err == nil {
+			for _, e := range flagVersions {
+				if e.IsDir() && validReleaseConfigName(e.Name()) {
+					ret = append(ret, e.Name())
+				}
+			}
+		}
+		return
+	}
+	m.FlagValueDirs = map[string][]string{
+		"aconfig":     subDirs("aconfig"),
+		"flag_values": subDirs("flag_values"),
+	}
+
 	err = WalkTextprotoFiles(dir, "release_configs", func(path string, d fs.DirEntry, err error) error {
 		releaseConfigContribution := &ReleaseConfigContribution{path: path, DeclarationIndex: ConfigDirIndex}
 		LoadMessage(path, &releaseConfigContribution.proto)
@@ -424,6 +443,27 @@
 		}
 	}
 
+	// Look for ignored flagging values.  Gather the entire list to make it easier to fix them.
+	errors := []string{}
+	for _, contrib := range configs.ReleaseConfigMaps {
+		dirName := filepath.Dir(contrib.path)
+		for k, names := range contrib.FlagValueDirs {
+			for _, rcName := range names {
+				if config, err := configs.GetReleaseConfig(rcName); err == nil {
+					rcPath := filepath.Join(dirName, "release_configs", fmt.Sprintf("%s.textproto", config.Name))
+					if _, err := os.Stat(rcPath); err != nil {
+						errors = append(errors, fmt.Sprintf("%s exists but %s does not contribute to %s",
+							filepath.Join(dirName, k, rcName), dirName, config.Name))
+					}
+				}
+
+			}
+		}
+	}
+	if len(errors) > 0 {
+		return fmt.Errorf("%s", strings.Join(errors, "\n"))
+	}
+
 	releaseConfig, err := configs.GetReleaseConfig(targetRelease)
 	if err != nil {
 		return err
diff --git a/cmd/release_config/release_config_lib/util.go b/cmd/release_config/release_config_lib/util.go
index 9919c70..b149293 100644
--- a/cmd/release_config/release_config_lib/util.go
+++ b/cmd/release_config/release_config_lib/util.go
@@ -31,8 +31,9 @@
 )
 
 var (
-	disableWarnings    bool
-	containerRegexp, _ = regexp.Compile("^[a-z][a-z0-9]*([._][a-z][a-z0-9]*)*$")
+	disableWarnings        bool
+	containerRegexp, _     = regexp.Compile("^[a-z][a-z0-9]*([._][a-z][a-z0-9]*)*$")
+	releaseConfigRegexp, _ = regexp.Compile("^[a-z][a-z0-9]*([._][a-z0-9]*)*$")
 )
 
 type StringList []string
@@ -179,6 +180,10 @@
 	return containerRegexp.MatchString(container)
 }
 
+func validReleaseConfigName(name string) bool {
+	return releaseConfigRegexp.MatchString(name)
+}
+
 // Returns the default value for release config artifacts.
 func GetDefaultOutDir() string {
 	outEnv := os.Getenv("OUT_DIR")
diff --git a/elf/Android.bp b/elf/Android.bp
index 6450be1..6d3f4f0 100644
--- a/elf/Android.bp
+++ b/elf/Android.bp
@@ -20,6 +20,7 @@
     name: "soong-elf",
     pkgPath: "android/soong/elf",
     srcs: [
+        "build_id_dir.go",
         "elf.go",
     ],
     testSrcs: [
diff --git a/elf/build_id_dir.go b/elf/build_id_dir.go
new file mode 100644
index 0000000..5fb7dda
--- /dev/null
+++ b/elf/build_id_dir.go
@@ -0,0 +1,172 @@
+// Copyright 2024 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package elf
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+func UpdateBuildIdDir(path string) error {
+	path = filepath.Clean(path)
+	buildIdPath := path + "/.build-id"
+
+	// Collect the list of files and build-id symlinks. If the symlinks are
+	// up to date (newer than the symbol files), there is nothing to do.
+	var buildIdFiles, symbolFiles []string
+	var buildIdMtime, symbolsMtime time.Time
+	filepath.WalkDir(path, func(path string, entry fs.DirEntry, err error) error {
+		if entry == nil || entry.IsDir() {
+			return nil
+		}
+		info, err := entry.Info()
+		if err != nil {
+			return err
+		}
+		mtime := info.ModTime()
+		if strings.HasPrefix(path, buildIdPath) {
+			if buildIdMtime.Compare(mtime) < 0 {
+				buildIdMtime = mtime
+			}
+			buildIdFiles = append(buildIdFiles, path)
+		} else {
+			if symbolsMtime.Compare(mtime) < 0 {
+				symbolsMtime = mtime
+			}
+			symbolFiles = append(symbolFiles, path)
+		}
+		return nil
+	})
+	if symbolsMtime.Compare(buildIdMtime) < 0 {
+		return nil
+	}
+
+	// Collect build-id -> file mapping from ELF files in the symbols directory.
+	concurrency := 8
+	done := make(chan error)
+	buildIdToFile := make(map[string]string)
+	var mu sync.Mutex
+	for i := 0; i != concurrency; i++ {
+		go func(paths []string) {
+			for _, path := range paths {
+				id, err := Identifier(path, true)
+				if err != nil {
+					done <- err
+					return
+				}
+				if id == "" {
+					continue
+				}
+				mu.Lock()
+				oldPath := buildIdToFile[id]
+				if oldPath == "" || oldPath > path {
+					buildIdToFile[id] = path
+				}
+				mu.Unlock()
+			}
+			done <- nil
+		}(symbolFiles[len(symbolFiles)*i/concurrency : len(symbolFiles)*(i+1)/concurrency])
+	}
+
+	// Collect previously generated build-id -> file mapping from the .build-id directory.
+	// We will use this for incremental updates. If we see anything in the .build-id
+	// directory that we did not expect, we'll delete it and start over.
+	prevBuildIdToFile := make(map[string]string)
+out:
+	for _, buildIdFile := range buildIdFiles {
+		if !strings.HasSuffix(buildIdFile, ".debug") {
+			prevBuildIdToFile = nil
+			break
+		}
+		buildId := buildIdFile[len(buildIdPath)+1 : len(buildIdFile)-6]
+		for i, ch := range buildId {
+			if i == 2 {
+				if ch != '/' {
+					prevBuildIdToFile = nil
+					break out
+				}
+			} else {
+				if (ch < '0' || ch > '9') && (ch < 'a' || ch > 'f') {
+					prevBuildIdToFile = nil
+					break out
+				}
+			}
+		}
+		target, err := os.Readlink(buildIdFile)
+		if err != nil || !strings.HasPrefix(target, "../../") {
+			prevBuildIdToFile = nil
+			break
+		}
+		prevBuildIdToFile[buildId[0:2]+buildId[3:]] = path + target[5:]
+	}
+	if prevBuildIdToFile == nil {
+		err := os.RemoveAll(buildIdPath)
+		if err != nil {
+			return err
+		}
+		prevBuildIdToFile = make(map[string]string)
+	}
+
+	// Wait for build-id collection from ELF files to finish.
+	for i := 0; i != concurrency; i++ {
+		err := <-done
+		if err != nil {
+			return err
+		}
+	}
+
+	// Delete old symlinks.
+	for id, _ := range prevBuildIdToFile {
+		if buildIdToFile[id] == "" {
+			symlinkDir := buildIdPath + "/" + id[:2]
+			symlinkPath := symlinkDir + "/" + id[2:] + ".debug"
+			if err := os.Remove(symlinkPath); err != nil {
+				return err
+			}
+		}
+	}
+
+	// Add new symlinks and update changed symlinks.
+	for id, path := range buildIdToFile {
+		prevPath := prevBuildIdToFile[id]
+		if prevPath == path {
+			continue
+		}
+		symlinkDir := buildIdPath + "/" + id[:2]
+		symlinkPath := symlinkDir + "/" + id[2:] + ".debug"
+		if prevPath == "" {
+			if err := os.MkdirAll(symlinkDir, 0755); err != nil {
+				return err
+			}
+		} else {
+			if err := os.Remove(symlinkPath); err != nil {
+				return err
+			}
+		}
+
+		target, err := filepath.Rel(symlinkDir, path)
+		if err != nil {
+			return err
+		}
+		if err := os.Symlink(target, symlinkPath); err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/ui/build/Android.bp b/ui/build/Android.bp
index ee286f6..fcf29c5 100644
--- a/ui/build/Android.bp
+++ b/ui/build/Android.bp
@@ -36,6 +36,7 @@
         "blueprint-bootstrap",
         "blueprint-microfactory",
         "soong-android",
+        "soong-elf",
         "soong-finder",
         "soong-remoteexec",
         "soong-shared",
diff --git a/ui/build/build.go b/ui/build/build.go
index 03d8392..c7319ed 100644
--- a/ui/build/build.go
+++ b/ui/build/build.go
@@ -22,6 +22,7 @@
 	"sync"
 	"text/template"
 
+	"android/soong/elf"
 	"android/soong/ui/metrics"
 )
 
@@ -344,6 +345,7 @@
 			installCleanIfNecessary(ctx, config)
 		}
 		runNinjaForBuild(ctx, config)
+		updateBuildIdDir(ctx, config)
 	}
 
 	if what&RunDistActions != 0 {
@@ -351,6 +353,16 @@
 	}
 }
 
+func updateBuildIdDir(ctx Context, config Config) {
+	ctx.BeginTrace(metrics.RunShutdownTool, "update_build_id_dir")
+	defer ctx.EndTrace()
+
+	symbolsDir := filepath.Join(config.ProductOut(), "symbols")
+	if err := elf.UpdateBuildIdDir(symbolsDir); err != nil {
+		ctx.Printf("failed to update %s/.build-id: %v", symbolsDir, err)
+	}
+}
+
 func evaluateWhatToRun(config Config, verboseln func(v ...interface{})) int {
 	//evaluate what to run
 	what := 0