Fixed three packages in GNU Guix:
156d81666b2 gnu: tracy-wayland: Fix build.
bedb96ad2e3 gnu: trueprint: Fix build.
ae7386f007c gnu: tlf: Fix build.

The common motive of those errors is that Guix now uses GCC 15 by default, while some packages use deprecated C/C++ features that are now marked in GCC as errors. A quick-fix for such errors is to use older GCC version (say, 13) in "native-inputs".

This can be a "low-hanging fruit" for those who want to make the first-time contribution to #Guix.