This makes cmake export the qmlls.ini settings for qmlls (lang server),
which makes it aware of the C++ components used in the project. By
default, qmlls wasn't able to find these as they lived in a separate
build dir which it didn't know about.
Additionally, this also enables exporting compile commands to provide
better support for other editors that rely on these. Note that the
compile_commands.json will still only be exported into the build dir
though, so to make use of this, you'll probably want to symlink this
from the build dir.
ItsDrike