fix oss build

Summary:
Two things
- Use thenValue instead of then in one specific occurrence as later one has been deprecated
- Build googletest on `release-1.8.1` as it is the one that compiles with c++11

Reviewed By: cenzhao

Differential Revision: D10178139

fbshipit-source-id: 069578716e5e55ef0a25ea87e9ef5ceded1ff9d6

build/fbcode_builder/specs/gmock.py

@@ -6,6 +6,7 @@ from __future__ import unicode_literals
 
 
 def fbcode_builder_spec(builder):
+    builder.add_option('google/googletest:git_hash', 'release-1.8.1')
     builder.add_option(
         'google/googletest:cmake_defines',
         {'BUILD_GTEST': 'ON'}