fbcode_builder: minor style cleanup in ThriftCppLibrary.cmake
fbcode_builder: minor style cleanup in ThriftCppLibrary.cmake

Summary:
Add explicit double quotes around arguments that are intended to be exactly a
single parameter.  Also line wrap to 80 characters.

Reviewed By: wez

Differential Revision: D16738443

fbshipit-source-id: b8c9b6d50da72b44e23eaf5effbc384b6cbbc1c0

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