rust: add aconfig_flag support

Bug: b/308625757
Test: manual
Change-Id: Ifd98cd0ad4e2525b08f5766e9332991c049162ea
diff --git a/rust/rust.go b/rust/rust.go
index 3d51a13..ddebb75 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -26,6 +26,7 @@
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 
+	"android/soong/aconfig"
 	"android/soong/android"
 	"android/soong/cc"
 	cc_config "android/soong/cc/config"
@@ -176,6 +177,9 @@
 	transitiveAndroidMkSharedLibs *android.DepSet[string]
 
 	android.BazelModuleBase
+
+	// Aconfig files for all transitive deps.  Also exposed via TransitiveDeclarationsInfo
+	mergedAconfigFiles map[string]android.Paths
 }
 
 func (mod *Module) Header() bool {
@@ -1006,6 +1010,8 @@
 	if mod.testModule {
 		ctx.SetProvider(testing.TestModuleProviderKey, testing.TestModuleProviderData{})
 	}
+
+	aconfig.CollectDependencyAconfigFiles(ctx, &mod.mergedAconfigFiles)
 }
 
 func (mod *Module) deps(ctx DepsContext) Deps {