dri3_glx.c includes xshmfence and glxcmds.c includes xf86vm, neither of
which are listed as dependencies of the glx lib in the meson.build file.
Consequently, those files would fail to compile on machines that did not
have xshmfence and xf86vm installed globally. This commit rectifies the
issue by adding the missing dependencies
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17585>