Fix and check CLANG_CONFIG_UNKNOWN_CFLAGS

Change-Id: Id8d4ab5e7bf7c9ed161596c19ccdfe00aaa2f7c6

cc/clang.go

@@ -15,6 +15,8 @@ var clangUnknownCflags = sorted([]string{
 	"-fno-tree-sra",
 	"-fprefetch-loop-arrays",
 	"-funswitch-loops",
+	"-Werror=unused-but-set-parameter",
+	"-Werror=unused-but-set-variable",
 	"-Wmaybe-uninitialized",
 	"-Wno-error=clobbered",
 	"-Wno-error=maybe-uninitialized",

cc/makevars.go

@@ -34,6 +34,7 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 	ctx.Strict("CLANG_CXX", "${clangBin}/clang++")
 	ctx.Strict("LLVM_AS", "${clangBin}/llvm-as")
 	ctx.Strict("LLVM_LINK", "${clangBin}/llvm-link")
+	ctx.StrictSorted("CLANG_CONFIG_UNKNOWN_CFLAGS", strings.Join(clangUnknownCflags, " "))
 
 	hostType := android.CurrentHostType()
 	arches := ctx.Config().HostArches[hostType]