I don't know what caused this, but something between Guix 0.14.0-6.0dcf675 and 0.14.0-8.bc880f9 forced my own computer attempt to build Emacs, and resulted in a working Emacs version.
Store path name differences for Emacs: - Old (working): b1nbgnpifkisz4szmasxrwzqlgqagy8w-emacs-25.3 - New (self-built, working): lh66vaxq3da6m8yz83lvgny4f4bwh760-emacs-25.3
