[asan] Add gcc 8's driver option -fsanitize=pointer-compare and -fsanitize=pointer-substract.

Disabled by default as this is still an experimental feature.

Reviewed By: thakis

Differential Revision: https://reviews.llvm.org/D59221

llvm-svn: 358285
diff --git a/clang/lib/Driver/ToolChains/CrossWindows.cpp b/clang/lib/Driver/ToolChains/CrossWindows.cpp
index 959dfd2..bd3a6e1 100644
--- a/clang/lib/Driver/ToolChains/CrossWindows.cpp
+++ b/clang/lib/Driver/ToolChains/CrossWindows.cpp
@@ -277,6 +277,8 @@
 clang::SanitizerMask CrossWindowsToolChain::getSupportedSanitizers() const {
   SanitizerMask Res = ToolChain::getSupportedSanitizers();
   Res |= SanitizerKind::Address;
+  Res |= SanitizerKind::PointerCompare;
+  Res |= SanitizerKind::PointerSubtract;
   return Res;
 }