Revert "[cmake] Fix a unittest when `LLVM_LINK_LLVM_DYLIB` is requested."
Revert "[cmake] Fix a unittest when `LLVM_LINK_LLVM_DYLIB` is requested."

This reverts commit r342150 as it caused test failure

    LLVM-Unit :: Passes/./PluginsTests/PluginsTests.LoadPlugin

on multiple bots.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@342169 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm