[WebAssembly] Add atomics target option

Reviewers: tlively

Subscribers: dschuff, sbc100, jgravelle-google, sunfish, jfb, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D57798

llvm-svn: 353260
diff --git a/clang/lib/Basic/Targets/WebAssembly.h b/clang/lib/Basic/Targets/WebAssembly.h
index 1d41f20..efd32c7 100644
--- a/clang/lib/Basic/Targets/WebAssembly.h
+++ b/clang/lib/Basic/Targets/WebAssembly.h
@@ -34,6 +34,7 @@
   bool HasSignExt = false;
   bool HasExceptionHandling = false;
   bool HasBulkMemory = false;
+  bool HasAtomics = false;
 
 public:
   explicit WebAssemblyTargetInfo(const llvm::Triple &T, const TargetOptions &)