[compiler-rt][cmake] Fix not lipo libclang_rt.cc_kext.a when building on OS X

Summary:

Fix r252525 - cmake configure failed to connect target builtins to target compiler-rt  because of early return call.

Patch by: Jacky Tsao (cao.zhong1)

Reviewers: beanz

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14747

llvm-svn: 253692