GN: Add option to build with TSAN

runtime/BUILD.gn

Index: runtime/BUILD.gn
diff --git a/runtime/BUILD.gn b/runtime/BUILD.gn
index 6008aecabad0430312d83ca6f0f48e5cbc0a6c30..9423429b74bf62eefe1e9d04dc168f3660da3832 100644
--- a/runtime/BUILD.gn
+++ b/runtime/BUILD.gn
@@ -168,8 +168,12 @@ config("dart_config") {
       cflags += [ "-O3" ]
     }
 
+    ldflags = []
     if (defined(is_asan) && is_asan) {
-      ldflags = [ "-fsanitize=address" ]
+      ldflags += [ "-fsanitize=address" ]
+    }
+    if (defined(is_tsan) && is_tsan) {
+      ldflags += [ "-fsanitize=thread" ]
     }

[siva, 2017/01/03 20:53:08]

should we also add support for MSAN while we are at it.

(needs options -fsanitize=memory -fPIC)

[zra, 2017/01/03 22:36:56]

Done.

   }
 }