Add flag to enable default clang builds--USE_CLANG_PLATFORM_BUILD.

bug 17007253

Change-Id: Ib11c017bf8aee384e6780e2a1252221fbff3327a
diff --git a/core/binary.mk b/core/binary.mk
index df176f1..437361b 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -151,6 +151,13 @@
     endif
 endif
 
+# Add option to make clang the default for device build
+ifeq ($(USE_CLANG_PLATFORM_BUILD),true)
+    ifeq ($(my_clang),)
+        my_clang := true
+    endif
+endif
+
 # arch-specific static libraries go first so that generic ones can depend on them
 my_static_libraries := $(LOCAL_STATIC_LIBRARIES_$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)) $(LOCAL_STATIC_LIBRARIES_$(my_32_64_bit_suffix)) $(my_static_libraries)
 my_whole_static_libraries := $(LOCAL_WHOLE_STATIC_LIBRARIES_$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)) $(LOCAL_WHOLE_STATIC_LIBRARIES_$(my_32_64_bit_suffix)) $(my_whole_static_libraries)