[CMake] Clang: Don't use object libraries with Xcode

Undoes some of the effects of r360946 when using the Xcode CMake
generator---it doesn't handle object libraries correctly at all.
Attempts to still honor BUILD_SHARED_LIBS for Xcode, but I didn't
actually test it. Should have no effect on non-Xcode generators.

https://reviews.llvm.org/D68430

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@373769 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed