Fix the unbundled mainline module build

This change fixes two problems:

1) the prebuilt apexes are force disabled for the unbundled builds
because we need to build the modules from the source then

2) the dependencies from an sdk_library module to
*.stubs.{public|system|tests} are not added for the unbundled build
because the stubs modules are disabled.

Bug: 137282010
Test: unbundled mainline builds are successful
Test: build com.android.media and inspect the jar file to see if
hiddenapi flags are there
$ cd out/dist/mainline_modules_arm
$ unzip com.android.media.apex apex_payload.img
$ mkdir -p mnt
$ sudo mount -o ro,loop apex_payload.img mnt
$ dexdump2 mnt/javalib/updatable-media.jar | grep hiddenapi
shows results

Merged-In: I2c00af07aac4a15770d3acab011a36e2e4803bfc
Change-Id: I2c00af07aac4a15770d3acab011a36e2e4803bfc

java/sdk_library.go

@@ -162,15 +162,20 @@ var _ Dependency = (*SdkLibrary)(nil)
 var _ SdkLibraryDependency = (*SdkLibrary)(nil)
 
 func (module *SdkLibrary) DepsMutator(ctx android.BottomUpMutatorContext) {
+	useBuiltStubs := !ctx.Config().UnbundledBuildUsePrebuiltSdks()
 	// Add dependencies to the stubs library
-	ctx.AddVariationDependencies(nil, publicApiStubsTag, module.stubsName(apiScopePublic))
+	if useBuiltStubs {
+		ctx.AddVariationDependencies(nil, publicApiStubsTag, module.stubsName(apiScopePublic))
+	}
 	ctx.AddVariationDependencies(nil, publicApiFileTag, module.docsName(apiScopePublic))
 
 	if !Bool(module.properties.No_standard_libs) {
-		ctx.AddVariationDependencies(nil, systemApiStubsTag, module.stubsName(apiScopeSystem))
+		if useBuiltStubs {
+			ctx.AddVariationDependencies(nil, systemApiStubsTag, module.stubsName(apiScopeSystem))
+			ctx.AddVariationDependencies(nil, testApiStubsTag, module.stubsName(apiScopeTest))
+		}
 		ctx.AddVariationDependencies(nil, systemApiFileTag, module.docsName(apiScopeSystem))
 		ctx.AddVariationDependencies(nil, testApiFileTag, module.docsName(apiScopeTest))
-		ctx.AddVariationDependencies(nil, testApiStubsTag, module.stubsName(apiScopeTest))
 	}
 
 	module.Library.deps(ctx)