Work around gcc's inability to compile an incomplete type in googletest,

leading to hundreds of lines of fairly unreadable error messages.

I don't think we particularly care about the specific source file gcc
dies on, and the many layers of macros and sub-types in googletest make
it very hard to diagnose whether this is a bug in googletest, gcc, clang
or libc++.

contrib/googletest/googlemock/test/gmock-spec-builders_test.cc

@@ -107,7 +107,8 @@ using testing::internal::CaptureStdout;
 using testing::internal::GetCapturedStdout;
 #endif
 
-class Incomplete;
+class Incomplete {
+};
 
 class MockIncomplete {
  public: