Get back to a -werror build
Glib is no more compiling with the
-werror option on its Unix CI tests, but it was the case a few years ago. The default build process on CI should be performed with
--werror --warnlevel 3 in order to catch the maximum amount of mistakes before a MR get accepted.
I have already submitted a few patches to achieve this and I will be keep going until the
--werror --warnlevel 3 is building Glib with no problem.