Convert filegroups in api_bp2build

api providing modules (droidstubs, cc_library etc.) can refer to the api
file via a separate filegroup module. Therefore these modules should be
generated in the api_bp2build workspace as well

Test: m api_bp2build && build/bazel/bin/bazel build
--config=api_bp2build --config=android //build/orchestrator/apis:*

Change-Id: I77371bd94a2794770b01b98aaf84b1bc42810841

android/filegroup.go

@@ -78,6 +78,12 @@ type bazelAidlLibraryAttributes struct {
 	Strip_import_prefix *string
 }
 
+// api srcs can be contained in filegroups.
+// this should be generated in api_bp2build workspace as well.
+func (fg *fileGroup) ConvertWithApiBp2build(ctx TopDownMutatorContext) {
+	fg.ConvertWithBp2build(ctx)
+}
+
 // ConvertWithBp2build performs bp2build conversion of filegroup
 func (fg *fileGroup) ConvertWithBp2build(ctx TopDownMutatorContext) {
 	srcs := bazel.MakeLabelListAttribute(