totem: disable parallel building

meson does not support parallel building of certain vala projects:
https://github.com/mesonbuild/meson/issues/1994
https://bugzilla.gnome.org/show_bug.cgi?id=784236

but at the moment this only affects gnome3.totem:

ninja src/plugins/rotation/rotation.vapi
[1/1] Compiling Vala source ../src/plugins/rotation/bacon-video.vapi ../src/plugins/rotation/totem-rotation-plugin.vala.
FAILED: src/plugins/rotation/rotation@sha/totem-rotation-plugin.c src/plugins/rotation/rotation.h src/plugins/rotation/rotation.vapi
valac -C --pkg clutter-gtk-1.0 --pkg cogl-pango-1.0 --pkg libpeas-1.0 --pkg gtk+-3.0 --color=always --directory src/plugins/rotation/rotation@sha --basedir ../src/plugins/rotation --library rotation --header src/plugins/rotation/rotation.h --vapi ../rotation.vapi --girdir=/tmp/nds-build-gnome3.totem/totem-3.26.0/build/src --pkg=Totem-1.0 ../src/plugins/rotation/bacon-video.vapi ../src/plugins/rotation/totem-rotation-plugin.vala
error: Package `Totem-1.0' not found in specified Vala API directories or GObject-Introspection GIR directories