cmake: fix build with CompilerRT
cmake: fix build with CompilerRT

A redefinition of append_if in CompilerRTUtils causes the append_if to fail.
Manually append the values to the flags.

Thanks to Kuba Ober for pointing this out!

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@204311 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb