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
diff --git a/cc/cc.go b/cc/cc.go
index dd73504..28354a8 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -106,6 +106,7 @@
 	YaccFlags   []string // Flags that apply to Yacc source files
 	protoFlags  []string // Flags that apply to proto source files
 	aidlFlags   []string // Flags that apply to aidl source files
+	rsFlags     []string // Flags that apply to renderscript source files
 	LdFlags     []string // Flags that apply to linker command lines
 	libFlags    []string // Flags to add libraries early to the link order
 	TidyFlags   []string // Flags that apply to clang-tidy