Change USE_CLANG_PLATFORM_BUILD default to true.

When USE_CLANG_PLATFORM_BUILD is not set, default will be clang/llvm.
USE_CLANG_PLATFORM_BUILD=false can be used to select gcc as default.

BUG: 23163853
BUG: 26102335

Change-Id: I00604c2aef4849e8c3505b2c4002eb1c46cd1fd1
diff --git a/core/binary.mk b/core/binary.mk
index 9ac609c..ddc4a1b 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -209,11 +209,13 @@
         my_clang := true
     endif
     endif
-# Add option to make clang the default for device build
-else ifeq ($(USE_CLANG_PLATFORM_BUILD),true)
+# Add option to make gcc the default for device build
+else ifeq ($(USE_CLANG_PLATFORM_BUILD),false)
     ifeq ($(my_clang),)
-        my_clang := true
+        my_clang := false
     endif
+else ifeq ($(my_clang),)
+    my_clang := true
 endif
 
 my_cpp_std_version := -std=gnu++14