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

nodakai/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman