Disable -Wthread-safety-negative

ART used to turn on -Wthread-safety-negative, but at some point the
build started adding -Wno-thread-safety-negative later on the command
line.  That is being fixed, but causes new warnings in ART.  Disable
-Wthread-safety-negative for now.

Bug: 144045034
Test: mma
Change-Id: I3a2edd4472b6ff7beff08289c45997694f543668
diff --git a/build/Android.bp b/build/Android.bp
index e2767ff..d686f34 100644
--- a/build/Android.bp
+++ b/build/Android.bp
@@ -81,7 +81,8 @@
 
         // Warn about thread safety violations with clang.
         "-Wthread-safety",
-        "-Wthread-safety-negative",
+        // TODO(b/144045034): turn on -Wthread-safety-negative
+        //"-Wthread-safety-negative",
 
         // Warn if switch fallthroughs aren't annotated.
         "-Wimplicit-fallthrough",