Fix cpp2 make_constant under gcc
Fix cpp2 make_constant under gcc

Summary: [Thrift] Fix cpp2 make_constant, which works under clang but not under (at least some versions of) gcc for reasons unknown. Just try a different strategy.

Reviewed By: philippv

Differential Revision: D17777111

fbshipit-source-id: efdd5c64d92461a5c8783daee576a8258e481302

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift