Tim-Philipp Müller authored Mar 23, 2017 and Emmanuele Bassi committed May 03, 2017

We have to work around some ordering problems here. We still
manage to keep most of the guts in modules/input/meson.build,
so it's not too ugly overall.

(The autotools build solves this with a 'make -C ../../input/modules'
inside gtk/Makefile, but that's not something we can or want to do.)