Fix building as a meson subproject

• When building dav1d as a dependency fallback, the parent project needs to provide the variable name of a dependency object, added dav1d_dep for that.
• SOURCE_ROOT is the root of the main project source tree, use current_source_dir() instead.

added buildsystem label

assigned to @ePirat

Hi, thanks for your work on this.

LGTM

added 12 commits

• d83819cb...115fe773 - 11 commits from branch videolan:master
• 50220456 - Fix building as a meson subproject

Compare with previous version

merged

changed milestone to %0.6.0