Update OSS CMakeLists.txt to use CMAKE_CXX_STANDARD

Summary: Adjust low level deps in OSS builds to use standard `CMAKE_CXX_STANDARD` variables to control std level in cpp builds.

Reviewed By: yfeldblum

Differential Revision: D23333713

fbshipit-source-id: cd76712d6b045f1d0aff30d4874d9bf0ce6f1e01

CMakeLists.txt

@@ -71,6 +71,9 @@ set(FOLLY_SUPPORT_SHARED_LIBRARY "${BUILD_SHARED_LIBS}")
 include(FBBuildOptions)
 fb_activate_static_library_option()
 
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
   # Check target architecture
   if (NOT CMAKE_SIZEOF_VOID_P EQUAL 8)