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
new test.
The first patch (compiler-rt) is committed:
http://llvm.org/viewvc/llvm-project?view=revision&revision=236055
The second patch (llvm) is out for review:
http://reviews.llvm.org/D9334