Add cross-referencing support for Rust

Bug: 222044478
Test: run TARGET_BUILD_VARIANT=userdebug TARGET_PRODUCT=cf_x86_64_phone XREF_CORPUS=googleplex-android.googlesource.com/codesearch/android build/soong/build_kzip.bash
Change-Id: Ia12eed53fafd0cbbbf2cc499fa20a0f5a40031de
diff --git a/rust/library.go b/rust/library.go
index 62eaefd..1286549 100644
--- a/rust/library.go
+++ b/rust/library.go
@@ -474,8 +474,9 @@
 	return flags
 }
 
-func (library *libraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) android.Path {
-	var outputFile, ret android.ModuleOutPath
+func (library *libraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
+	var outputFile android.ModuleOutPath
+	var ret buildOutput
 	var fileName string
 	srcPath := library.srcPath(ctx, deps)
 
@@ -487,19 +488,19 @@
 	if library.rlib() {
 		fileName = library.getStem(ctx) + ctx.toolchain().RlibSuffix()
 		outputFile = android.PathForModuleOut(ctx, fileName)
-		ret = outputFile
+		ret.outputFile = outputFile
 	} else if library.dylib() {
 		fileName = library.getStem(ctx) + ctx.toolchain().DylibSuffix()
 		outputFile = android.PathForModuleOut(ctx, fileName)
-		ret = outputFile
+		ret.outputFile = outputFile
 	} else if library.static() {
 		fileName = library.getStem(ctx) + ctx.toolchain().StaticLibSuffix()
 		outputFile = android.PathForModuleOut(ctx, fileName)
-		ret = outputFile
+		ret.outputFile = outputFile
 	} else if library.shared() {
 		fileName = library.sharedLibFilename(ctx)
 		outputFile = android.PathForModuleOut(ctx, fileName)
-		ret = outputFile
+		ret.outputFile = outputFile
 	}
 
 	if !library.rlib() && !library.static() && library.stripper.NeedsStrip(ctx) {
@@ -524,13 +525,13 @@
 
 	// Call the appropriate builder for this library type
 	if library.rlib() {
-		TransformSrctoRlib(ctx, srcPath, deps, flags, outputFile)
+		ret.kytheFile = TransformSrctoRlib(ctx, srcPath, deps, flags, outputFile).kytheFile
 	} else if library.dylib() {
-		TransformSrctoDylib(ctx, srcPath, deps, flags, outputFile)
+		ret.kytheFile = TransformSrctoDylib(ctx, srcPath, deps, flags, outputFile).kytheFile
 	} else if library.static() {
-		TransformSrctoStatic(ctx, srcPath, deps, flags, outputFile)
+		ret.kytheFile = TransformSrctoStatic(ctx, srcPath, deps, flags, outputFile).kytheFile
 	} else if library.shared() {
-		TransformSrctoShared(ctx, srcPath, deps, flags, outputFile)
+		ret.kytheFile = TransformSrctoShared(ctx, srcPath, deps, flags, outputFile).kytheFile
 	}
 
 	if library.rlib() || library.dylib() {
@@ -572,7 +573,7 @@
 	return ret
 }
 
-func (library *libraryDecorator) srcPath(ctx ModuleContext, deps PathDeps) android.Path {
+func (library *libraryDecorator) srcPath(ctx ModuleContext, _ PathDeps) android.Path {
 	if library.sourceProvider != nil {
 		// Assume the first source from the source provider is the library entry point.
 		return library.sourceProvider.Srcs()[0]