swift234

[cmake] Instead of figuring out the exact location of all of the various libraries when translating Xcode targets, just use the path already provided in LLVMConfig.cmake for the configuration that we compiled LLVM specifically for.

If we compile LLVM for <CONFIG> in build-script with Xcode as our generator,
LLVMExports.cmake will have specific IMPORTED_*_<CONFIG> variables set for all
of our targets. These variables are what we really want to splat across all
Swift Xcode build configurations.

This patch rips out the old code that determined the actual location and instead
just grabs the IMPORTED_*_<CONFIG> variables and splats it accordingly.