Switch host builds to use Clang by default.

If LOCAL_CLANG is not set to false for a host module, clang will be used instead of gcc.

This also enables the integrated assembler by default for Darwin host builds.

bug 16172793

Change-Id: If7484c5dbcccce7d925bec97bff0a3e4c30e9434
diff --git a/core/clang/HOST_x86.mk b/core/clang/HOST_x86.mk
index 510a74d..fb5cbf4 100644
--- a/core/clang/HOST_x86.mk
+++ b/core/clang/HOST_x86.mk
@@ -11,6 +11,10 @@
 endif
 ifeq ($(HOST_OS),darwin)
 CLANG_CONFIG_x86_HOST_TRIPLE := i686-apple-darwin
+CLANG_CONFIG_x86_HOST_COMBO_EXTRA_ASFLAGS := $(CLANG_CONFIG_x86_DARWIN_HOST_EXTRA_ASFLAGS)
+CLANG_CONFIG_x86_HOST_COMBO_EXTRA_CFLAGS := $(CLANG_CONFIG_x86_DARWIN_HOST_EXTRA_CFLAGS)
+CLANG_CONFIG_x86_HOST_COMBO_EXTRA_CPPFLAGS := $(CLANG_CONFIG_x86_DARWIN_HOST_EXTRA_CPPFLAGS)
+CLANG_CONFIG_x86_HOST_COMBO_EXTRA_LDFLAGS := $(CLANG_CONFIG_x86_DARWIN_HOST_EXTRA_LDFLAGS)
 endif
 ifeq ($(HOST_OS),windows)
 CLANG_CONFIG_x86_HOST_TRIPLE := i686-pc-mingw32