Fixup for r188058: assume hasAsanZeroBaseShadow() is false if ASan is not needed

llvm-svn: 188068
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 8851316..9351e51 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -193,6 +193,8 @@
 }
 
 bool SanitizerArgs::hasAsanZeroBaseShadow(const ToolChain &TC) const {
+  if (!needsAsanRt())
+    return false;
   if (AsanZeroBaseShadow != AZBSK_Default)
     return AsanZeroBaseShadow == AZBSK_On;
   // Zero-base shadow is used by default only on Android.