getdeps: if the hash has changed, force a cmake reconfigure
getdeps: if the hash has changed, force a cmake reconfigure

Summary:
This is needed to correctly pick up changes made to
eg: cmake.defines sections in the manifest for first-party
projects.

Reviewed By: strager

Differential Revision: D15246337

fbshipit-source-id: 35e525e885f87d6136d5ff3b94ebf34516ab947c

rsocket/rsocket-cpp,phoad/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,ReactiveSocket/reactivesocket-cpp,phoad/rsocket-cpp,phoad/rsocket-cpp,rsocket/rsocket-cpp,phoad/rsocket-cpp,rsocket/rsocket-cpp,rsocket/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,phoad/rsocket-cpp