<issue_start><issue_comment>Title: Use the target as namebase for Vala
username_0: The first file name is actually used, but that's an incorrect assumption. Both VAPI and C header should be named based on the target name.

https://github.com/mesonbuild/meson/blob/16b3e220167e78a73810c46309f510459b698767/mesonbuild/backend/ninjabackend.py#L808<issue_closed>