Revert "Change USE_CLANG_PLATFORM_BUILD default to true."

This reverts commit 3c8036da538bbbf259ae4d56cc808943398cc45b.

Change-Id: I930bbebce8396d7c0abd847530640a696d3418e7
diff --git a/core/binary.mk b/core/binary.mk
index ddc4a1b..9ac609c 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -209,13 +209,11 @@
         my_clang := true
     endif
     endif
-# Add option to make gcc the default for device build
-else ifeq ($(USE_CLANG_PLATFORM_BUILD),false)
+# Add option to make clang the default for device build
+else ifeq ($(USE_CLANG_PLATFORM_BUILD),true)
     ifeq ($(my_clang),)
-        my_clang := false
+        my_clang := true
     endif
-else ifeq ($(my_clang),)
-    my_clang := true
 endif
 
 my_cpp_std_version := -std=gnu++14