This change is the third of 3 patches to add support for specifying
the profile output from the command line via -fprofile-instr-generate=<path>,
where the specified output path/file will be overridden by the
LLVM_PROFILE_FILE environment variable.
This patch adds the necessary support to the clang frontend, and adds a
The first patch (compiler-rt) is committed:
The second patch (llvm) is out for review: