The xorg-server-xwayland-21.1.0 package is broken on the
core-updates-frozen branch. The build succeeds, but the file
"bin/Xwayland" is missing in the result. Then the mutter package
depending on xorg-server-xwayland fails to build because it can't find
the Xwayland program.

According to the configure phase, xorg-server 21.1.0 doesn't understand
the "--enable-xwayland" option:

--8<---------------cut here---------------start------------->8---
config.status: executing sdksyms commands
configure: WARNING: unrecognized options: --enable-xwayland, --with-os-name, --with-os-vendor
phase `configure' succeeded after 6.6 seconds
--8<---------------cut here---------------end--------------->8---