Add bp2build arch-specific paths mutator

Adds deps for properties tagged `android:"path"` within arch, multilib,
and target properties.

Test: build/bazel/ci/bp2build.sh
Test: m nothing
Bug: 185217298
Change-Id: I0230da399d2c4e984b837f69523fa09eadba3ff1
diff --git a/android/arch.go b/android/arch.go
index 9f93752..a63d630 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -412,6 +412,54 @@
 	}
 }
 
+func registerBp2buildArchPathDepsMutator(ctx RegisterMutatorsContext) {
+	ctx.BottomUp("bp2build-arch-pathdeps", bp2buildArchPathDepsMutator).Parallel()
+}
+
+// add dependencies for architecture specific properties tagged with `android:"path"`
+func bp2buildArchPathDepsMutator(ctx BottomUpMutatorContext) {
+	var module Module
+	module = ctx.Module()
+
+	m := module.base()
+	if !m.ArchSpecific() {
+		return
+	}
+
+	// addPathDepsForProps does not descend into sub structs, so we need to descend into the
+	// arch-specific properties ourselves
+	properties := []interface{}{}
+	for _, archProperties := range m.archProperties {
+		for _, archProps := range archProperties {
+			archPropValues := reflect.ValueOf(archProps).Elem()
+			// there are three "arch" variations, descend into each
+			for _, variant := range []string{"Arch", "Multilib", "Target"} {
+				// The properties are an interface, get the value (a pointer) that it points to
+				archProps := archPropValues.FieldByName(variant).Elem()
+				if archProps.IsNil() {
+					continue
+				}
+				// And then a pointer to a struct
+				archProps = archProps.Elem()
+				for i := 0; i < archProps.NumField(); i += 1 {
+					f := archProps.Field(i)
+					// If the value of the field is a struct (as opposed to a pointer to a struct) then step
+					// into the BlueprintEmbed field.
+					if f.Kind() == reflect.Struct {
+						f = f.FieldByName("BlueprintEmbed")
+					}
+					if f.IsZero() {
+						continue
+					}
+					props := f.Interface().(interface{})
+					properties = append(properties, props)
+				}
+			}
+		}
+	}
+	addPathDepsForProps(ctx, properties)
+}
+
 // osMutator splits an arch-specific module into a variant for each OS that is enabled for the
 // module.  It uses the HostOrDevice value passed to InitAndroidArchModule and the
 // device_supported and host_supported properties to determine which OsTypes are enabled for this
@@ -899,13 +947,17 @@
 		if string(field.Tag) != `android:"`+strings.Join(values, ",")+`"` {
 			panic(fmt.Errorf("unexpected tag format %q", field.Tag))
 		}
+		// don't delete path tag as it is needed for bp2build
 		// these tags don't need to be present in the runtime generated struct type.
-		values = RemoveListFromList(values, []string{"arch_variant", "variant_prepend", "path"})
-		if len(values) > 0 {
+		values = RemoveListFromList(values, []string{"arch_variant", "variant_prepend"})
+		if len(values) > 0 && values[0] != "path" {
 			panic(fmt.Errorf("unknown tags %q in field %q", values, prefix+field.Name))
+		} else if len(values) == 1 {
+			field.Tag = reflect.StructTag(`android:"` + strings.Join(values, ",") + `"`)
+		} else {
+			field.Tag = ``
 		}
 
-		field.Tag = ""
 		return true, field
 	}
 	return false, field
diff --git a/android/arch_test.go b/android/arch_test.go
index 633ddaa..3aa4779 100644
--- a/android/arch_test.go
+++ b/android/arch_test.go
@@ -66,9 +66,9 @@
 			}{},
 			out: &struct {
 				A *string
-				B *string
-				C *string
-				D *string
+				B *string `android:"path"`
+				C *string `android:"path"`
+				D *string `android:"path"`
 			}{},
 			filtered: true,
 		},
diff --git a/android/bazel.go b/android/bazel.go
index 1f7f7e6..9806acc 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -151,7 +151,7 @@
 		"libc_bionic_ndk",               // ruperts@, cc_library_static, depends on //bionic/libc/system_properties
 		"libc_bionic_systrace",          // ruperts@, cc_library_static, 'private/bionic_systrace.h' file not found
 		"libc_pthread",                  // ruperts@, cc_library_static, 'private/bionic_defs.h' file not found
-		"libc_syscalls",                 // ruperts@, cc_library_static, mutator panic cannot get direct dep syscalls-arm64.S of libc_syscalls
+		"libc_syscalls",                 // eakammer@, cc_library_static,  'private/bionic_asm.h' file not found
 		"libc_ndk",                      // ruperts@, cc_library_static, depends on //bionic/libm:libm
 		"libc_nopthread",                // ruperts@, cc_library_static, depends on //external/arm-optimized-routines
 		"libc_common",                   // ruperts@, cc_library_static, depends on //bionic/libc:libc_nopthread
diff --git a/android/mutator.go b/android/mutator.go
index e25e2e8..365bf29 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -55,6 +55,7 @@
 	bp2buildDepsMutators = append([]RegisterMutatorFunc{
 		registerDepsMutatorBp2Build,
 		registerPathDepsMutator,
+		registerBp2buildArchPathDepsMutator,
 	}, depsMutators...)
 
 	for _, f := range bp2buildDepsMutators {
diff --git a/android/path_properties.go b/android/path_properties.go
index 2c8d27c..4446773 100644
--- a/android/path_properties.go
+++ b/android/path_properties.go
@@ -34,7 +34,10 @@
 // ":module" module reference syntax in a property that is tagged with `android:"path"`.
 func pathDepsMutator(ctx BottomUpMutatorContext) {
 	props := ctx.Module().base().generalProperties
+	addPathDepsForProps(ctx, props)
+}
 
+func addPathDepsForProps(ctx BottomUpMutatorContext, props []interface{}) {
 	// Iterate through each property struct of the module extracting the contents of all properties
 	// tagged with `android:"path"`.
 	var pathProperties []string