Check explicitly for exclude-file-list support (#1)

Some compilers (eg clang) support the GCC -finstrument-functions
extension, but not -finstrument-functions-exclude-file-list.

Note, we will need to protect the __cyg_profile_func_* functions
against infinit recursion for compilers (such as clang) that do not
support -finstrument-functions-exclude-file-list.