The fix for PR 85222 ends up generating duplicate debuginfo sections,
because we compile the .cc file and then compile the .s file. This
adds -g0 to the second step so we don't generate debuginfo again.

I've verified that we still have debuginfo for the file and can step
through the code when using the $prefix/lib64/debug/libstdc++.so.6
version of the library.

2018-04-18  Jonathan Wakely  <jwakely@redhat.com>
                Jakub Jelinek  <jakub@redhat.com>

            PR libstdc++/85442
            * src/c++11/Makefile.am: Don't generate debuginfo again for
            cxx11-ios_failure-lt.s and cxx11-ios_failure.s files.
            * src/c++11/Makefile.in: Regenerate.

Tested powerpc64le-linux, committed to trunk. Backport to gcc-7-branch
to follow.