gitlab-foss fails to build while installing rugged

Summary

I'm the Arch Linux maintainer for Gitlab. Versions > 12.5.1 have started failing to build.

Steps to reproduce

Try to run the build steps:

  bundle-2.5 config build.gpgme --use-system-libraries
  bundle-2.5 install --no-cache --deployment --without development test aws kerberos

  yarn install --production --pure-lockfile
  bundle-2.5 exec rake gitlab:assets:compile RAILS_ENV=production NODE_ENV=production NODE_OPTIONS="--max_old_space_size=4096"
  bundle-2.5 exec rake gettext:compile RAILS_ENV=production

See build instructions here: https://git.archlinux.org/svntogit/community.git/tree/trunk/PKGBUILD?h=packages/gitlab

All logs are attached

makepkg.log mkmf.log

The log mentions pthread not being found as a problem though it's definitely installed. Also to note, 12.5.1 compiled just fine.