make: Silence some xelatex output
Currently build logs from GitLab CI around around 7 megabytes each. Of this,
around 2 megabytes is latex output. This is quite silly as essentially all of
this output is unresolved references in the early latex iterations.
Here we silence this output.
However, to make sure that we don't silence errors we allow each xelatex
invocation besides the last to fail.