Test for _WIN32 in frameworks/compile/libbcc instead of USE_MINGW.

Bug: http://b/23392815
Test: builds
Change-Id: I248d1afed2510d9cbb73a0de9d97b8b95644be11
diff --git a/lib/Renderscript/RSCompilerDriver.cpp b/lib/Renderscript/RSCompilerDriver.cpp
index 1dfc699..f288810 100644
--- a/lib/Renderscript/RSCompilerDriver.cpp
+++ b/lib/Renderscript/RSCompilerDriver.cpp
@@ -152,7 +152,7 @@
   {
     // FIXME(srhines): Windows compilation can't use locking like this, but
     // we also don't need to worry about concurrent writers of the same file.
-#ifndef USE_MINGW
+#ifndef _WIN32
     //===------------------------------------------------------------------===//
     // Acquire the write lock for writing output object file.
     //===------------------------------------------------------------------===//