On Thu, 30 May 2019 at 19:43, Eli Zaretskii <eliz@gnu.org> wrote:

    We need to augment nt/mingw-cfg.site to bypass pthread_sigmask, there
    are already some settings there to that effect, we need to adapt them
    to this Gnulib change.  Maybe try adding this line to mingw-cfg.site:

      gl_cv_func_pthread_sigmask_macro=no

Yes, that works. (The build succeeds and no pthread_sigmask.o is generated.)
I'm impressed, thanks.

    If that doesn't help, please show the relevant parts of your
    config.log.  Anything that matches "pthread".

    (On my box the problem doesn't happen because I don't have the
    pthread.h header polluting my system.)

One package's pollution is another's prerequisite. Easily eradicated:

pacman -R ${MINGW_PACKAGE_PREFIX}-libwinpthread-git