[CMake] Use CMAKE_OBJCOPY and CMAKE_STRIP to externalize debug info
[CMake] Use CMAKE_OBJCOPY and CMAKE_STRIP to externalize debug info

Don't hardcode objcopy and strip names, rather use CMAKE_OBJCOPY and
CMAKE_STRIP variables which allows users to override the tools used
such as using llvm-objcopy and llvm-strip instead of binutils versions.

Differential Revision: https://reviews.llvm.org/D46611

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@331827 91177308-0d34-0410-b5e6-96231b3b80d8

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