Support .rs and .fs files in cc_* module srcs lists

Translate .rs and .fs files to .cpp files using llvm-rs-cc.

Test: builds
Change-Id: I242cea0d09c9985730a512cec7705c3f1479f4ed

cc/util.go

@@ -96,6 +96,7 @@ func flagsToBuilderFlags(in Flags) builderFlags {
 		yaccFlags:   strings.Join(in.YaccFlags, " "),
 		protoFlags:  strings.Join(in.protoFlags, " "),
 		aidlFlags:   strings.Join(in.aidlFlags, " "),
+		rsFlags:     strings.Join(in.rsFlags, " "),
 		ldFlags:     strings.Join(in.LdFlags, " "),
 		libFlags:    strings.Join(in.libFlags, " "),
 		tidyFlags:   strings.Join(in.TidyFlags, " "),