I see this fixed by commit

commit f448ded3a79dccfc1a95f032aa80ab228c2c7a09 (HEAD -> master, pgrpms/master)
Author: John K. Harvey <john.harvey@crunchydata.com>
Date:   Wed Aug 15 15:32:56 2018 -0400

    Fix broken PGXS=1 builds in -devel package (missing pg_config.h error)


so thanks. Unclear if you noticed this independently or from my mail, but either way, thanks.