[llvm-objcopy] - Fix the strip-dwo-groups.test.
[llvm-objcopy] - Fix the strip-dwo-groups.test.

It was reported (https://reviews.llvm.org/D65273#1612246)
that this test fails if the compilation directory contain
a "debug_" substring.

This should fix it.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@367702 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm