Fix hangs with Pango 1.48.3 and jobs
Pango 1.48.3 started spawning threads to offload FontConfig calls.
These threads hold locks, which is problematic when we call fork()
without exec()
because the child has only one thread, but the locks
remain "acquired". Prevent this kind of situation by moving the call
to ly_reset_all_fonts
into Scheme, after the fork
.
Fixes #6105 (closed)