Backport of "meson.build: use join_paths() on prefix" into 1.16
Backport of !294 (merged) "meson.build: use join_paths() on prefix".
Commits:
- 2572f4d7 meson.build: use join_paths() on prefix
Backport of !294 (merged) "meson.build: use join_paths() on prefix".
Commits: