buildsystem_changes.patch

diff --git a/test/libcxx/test/config.py b/test/libcxx/test/config.py
index 6c52880..f1d60a3 100644
--- a/test/libcxx/test/config.py
+++ b/test/libcxx/test/config.py
@@ -98,6 +98,7 @@ class Configuration(object):
         self.configure_cxx_library_root()
         self.configure_use_system_cxx_lib()
         self.configure_use_clang_verify()
+        self.configure_use_thread_safety()
         self.configure_execute_external()
         self.configure_ccache()
         self.configure_compile_flags()
@@ -218,6 +219,13 @@ class Configuration(object):
             self.lit_config.note(
                 "inferred use_clang_verify as: %r" % self.use_clang_verify)
 
+    def configure_use_thread_safety(self):
+        has_thread_safety = self.cxx.hasCompileFlag('-Werror=thread-safety')
+        if has_thread_safety:
+            self.cxx.compile_flags += ['-Werror=thread-safety']
+            self.config.available_features.add('thread-safety')
+            self.lit_config.note("enabling thread-safety annotations")
+
     def configure_execute_external(self):
         # Choose between lit's internal shell pipeline runner and a real shell.
         # If LIT_USE_INTERNAL_SHELL is in the environment, we use that as the
diff --git a/test/libcxx/test/format.py b/test/libcxx/test/format.py
index c21118a..865869a 100644
--- a/test/libcxx/test/format.py
+++ b/test/libcxx/test/format.py
@@ -167,7 +167,7 @@ class LibcxxTestFormat(object):
         # when using Clang.
         extra_flags = []
         if self.cxx.type != 'gcc':
-            extra_flags += ['-fsyntax-only', '-Werror=thread-safety']
+            extra_flags += ['-fsyntax-only']
         if use_verify:
             extra_flags += ['-Xclang', '-verify',
                             '-Xclang', '-verify-ignore-unexpected=note']