[Bug lto/105877] New: GNU strip breaks -flto -g .o files

["slyfox at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105877

            Bug ID: 105877
           Summary: GNU strip breaks -flto -g .o files
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at gcc dot gnu.org
                CC: hjl.tools at gmail dot com, hubicka at gcc dot gnu.org,
                    marxin at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-unknown-linux-gnu

Initially reported by drnfc on
https://github.com/trofi/nix-guix-gentoo/issues/19 where gcc failed to link
nix-2.9.0 against stripped liblowdown.a. Both are built with -flto.

I'm not sure if it's a strip bug, gcc bug or both. I think (did not check) it
used to work long ago. I'm leaning towards gcc bug and filing it here first.

Here is a minimal reproducer:

    // $ cat document.c
    void lowdown_doc_new(void) {}

    // $ cat markdown.cc
    extern "C" { void lowdown_doc_new(void); }
    int main(){ lowdown_doc_new(); }

    $ gcc -flto -g -c -o document.o document.c
    $ cp document.o document-stripped.o
    $ strip -g document-stripped.o
    $ g++ markdown.cc -o a document.o -flto-partition=max -flto -g
    $ g++ markdown.cc -o a document-stripped.o -flto-partition=max -flto -g
    ld: /tmp/ccajK6YG.ltrans0.ltrans.o:(.debug_info+0x2f): undefined reference
to `document.c.20ce96f1'

$ gcc -v |& unnix
Using built-in specs.
COLLECT_GCC=/<<NIX>>/gcc-13.0.0/bin/gcc
COLLECT_LTO_WRAPPER=/<<NIX>>/gcc-13.0.0/libexec/gcc/x86_64-unknown-linux-gnu/13.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with:
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.0.0 20220605 (experimental) (GCC)