build: Include the right things

build: Include the right things

If we build our own targets, we need to include those.

This is only relevant when adding new shaders because meson will
complain that the (unused) sources don't exist as it tries to include
those.
And that will make the build.ninja file not be generated which would
have build those shaders and would have allowed to copy them into the
sources.

Note that this makes builds with glslc not care about all the shader
files being included with the sources, but we have CI to check that.