Suppress deprecation warnings in related tests

Summary:
[Folly] Suppress deprecation warnings in related tests.

When a test specifically exercises a marked-deprecated library or a marked-deprecated part of a library, we do not need to see the deprecation warnings - they are noise.

Specifically, `Singleton` and `Subprocess` have tested but marked-deprecated APIs, so we suppress deprecation warnings in those specific test suites.

Reviewed By: andrewjcg

Differential Revision: D4230826

fbshipit-source-id: 937b078029cde492906088caa3a9e5eee449bc12

folly/test/SingletonBenchmark.cpp

@@ -24,6 +24,8 @@
 #include <folly/Memory.h>
 #include <folly/portability/GFlags.h>
 
+FOLLY_GCC_DISABLE_WARNING(deprecated-declarations)
+
 using namespace folly;
 
 // Benchmarking a normal singleton vs a Meyers singleton vs a Folly

folly/test/SingletonTest.cpp

@@ -30,6 +30,8 @@
 #include <glog/logging.h>
 #include <boost/thread/barrier.hpp>
 
+FOLLY_GCC_DISABLE_WARNING(deprecated-declarations)
+
 using namespace folly;
 
 TEST(Singleton, MissingSingleton) {

folly/test/SubprocessTest.cpp

@@ -33,6 +33,8 @@
 #include <folly/portability/GTest.h>
 #include <folly/portability/Unistd.h>
 
+FOLLY_GCC_DISABLE_WARNING(deprecated-declarations)
+
 using namespace folly;
 
 TEST(SimpleSubprocessTest, ExitsSuccessfully) {