[Bug libfortran/117834] New: libgfortran doesn't compile unless `PTHREAD_RWLOCK_INITIALIZER` is defined

[glex.spb at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117834

            Bug ID: 117834
           Summary: libgfortran doesn't compile unless
                    `PTHREAD_RWLOCK_INITIALIZER` is defined
           Product: gcc
           Version: 14.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glex.spb at gmail dot com
  Target Milestone: ---

Build error on macOS 10.4 (Tiger) PowerPC, which does not have this macro
defined:

```
:info:build In file included from
/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/gcc-14.2.0/libgfortran/../libgcc/gthr.h:157,
:info:build                  from
/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/gcc-14.2.0/libgfortran/io/io.h:33,
:info:build                  from
/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/gcc-14.2.0/libgfortran/io/unit.c:26:
:info:build ../libgcc/gthr-default.h:65:31: error: 'PTHREAD_RWLOCK_INITIALIZER'
undeclared here (not in a function); did you mean 'PTHREAD_COND_INITIALIZER'?
:info:build    65 | #define __GTHREAD_RWLOCK_INIT PTHREAD_RWLOCK_INITIALIZER
:info:build       |                               ^~~~~~~~~~~~~~~~~~~~~~~~~~
:info:build
/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/gcc-14.2.0/libgfortran/io/unit.c:107:34:
note: in expansion of macro '__GTHREAD_RWLOCK_INIT'
:info:build   107 | __gthread_rwlock_t unit_rwlock = __GTHREAD_RWLOCK_INIT;
:info:build       |                                  ^~~~~~~~~~~~~~~~~~~~~
:info:build make[3]: *** [io/unit.lo] Error 1
:info:build make[3]: Leaving directory
`/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/build/powerpc-apple-darwin8/libgfortran'
:info:build make[2]: *** [all] Error 2
:info:build make[2]: Leaving directory
`/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/build/powerpc-apple-darwin8/libgfortran'
:info:build make[1]: *** [all-target-libgfortran] Error 2
:info:build make[1]: Leaving directory
`/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/build'
:info:build make: *** [bootstrap-lean] Error 2
:info:build make: Leaving directory
`/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/build'
:info:build Command failed:  cd
"/opt/local/var/macports/build/_Users_andersjenbo_macports-ports_lang_gcc14/libgcc14/work/build"
&& /usr/bin/make -w bootstrap-lean 
:info:build Exit code: 2
```

This looks similar to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94069