Filter out gcc flags that are not recognized by clang.

Change-Id: I04e95fc3b0cb2825bf90a55916f89d25fa9fc475
diff --git a/core/clang/config.mk b/core/clang/config.mk
index ba48f63..13a5ba1 100644
--- a/core/clang/config.mk
+++ b/core/clang/config.mk
@@ -68,14 +68,18 @@
   -funswitch-loops \
   -Wmaybe-uninitialized \
   -Wno-error=maybe-uninitialized \
+  -Wno-error=unused-but-set-parameter \
+  -Wno-error=unused-but-set-variable \
   -Wno-free-nonheap-object \
   -Wno-literal-suffix \
   -Wno-maybe-uninitialized \
   -Wno-old-style-declaration \
   -Wno-psabi \
-  -Wno-unused-but-set-variable \
   -Wno-unused-but-set-parameter \
-  -Wno-unused-local-typedefs
+  -Wno-unused-but-set-variable \
+  -Wno-unused-local-typedefs \
+  -Wunused-but-set-parameter \
+  -Wunused-but-set-variable
 
 # Clang flags for all host rules
 CLANG_CONFIG_HOST_EXTRA_ASFLAGS :=