Yes, in May, and in October, each time to upgrade and build my externals. However, I did just an MSys2 upgrade yesterday out of an excess urge of up-to-date-ness. Having tried all the combinations now, I don;t seem to have a PD-buildable environment anywhere, so I guess it's time for the standard Windows solution of deleting everything and reinstalling.
Thank you for the help. If I still have problems after the clean-down, I'll let you know.
GPG Public key at
http://cyber-rush.org/drr/gpg-public-key.txt