Reduce warning spam from "unused-" flags in //external, //vendor, //hardware

Some clang unused-* warnings are not covered by "-Wno-unused". Add them
explicitly to avoid noise from these warnings, given that they don't
generally get fixed.

Test: Local clean builds.
Change-Id: I13f5089fd68f1a67a11be14fa41807688d803ba3
diff --git a/cc/config/global.go b/cc/config/global.go
index 5fed7f1..338c0e3 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -351,7 +351,8 @@
 		// enabling since it's a cosmetic issue.
 		"-Wno-bitwise-instead-of-logical",
 
-		"-Wno-unused-but-set-variable",
+		"-Wno-unused",
+		"-Wno-unused-parameter",
 		"-Wno-unused-but-set-parameter",
 		"-Wno-unqualified-std-cast-call",
 		"-Wno-array-parameter",