Test for _WIN32 in instead of USE_MINGW.

Bug: http://b/23392815
Test: builds
Change-Id: I7fce8de1f0e2314170cce456cd49346dcee9d134
diff --git a/libutils/Printer.cpp b/libutils/Printer.cpp
index 1dc8632..98cd2c6 100644
--- a/libutils/Printer.cpp
+++ b/libutils/Printer.cpp
@@ -44,7 +44,7 @@
 
     char* formattedString;
 
-#ifndef USE_MINGW
+#ifndef _WIN32
     if (vasprintf(&formattedString, format, arglist) < 0) { // returns -1 on error
         ALOGE("%s: Failed to format string", __FUNCTION__);
         return;
@@ -115,7 +115,7 @@
         return;
     }
 
-#ifndef USE_MINGW
+#ifndef _WIN32
     dprintf(mFd, mFormatString, mPrefix, string);
 #endif
 }