This code cleverly tried to use a fancy new pathlib.Path method to get
the os.path.commonpath of two paths and check whether one is inside the
other. It failed pretty badly, because of a hidden secret of pathlib: it
is designed to throw random exceptions at all times (except when
building os.PathLike interfaces) instead of performing useful work.
Return to `os.path`.
In particular, before this change, we wanted to check if files are NOT
in a subpath of `preserve_path_from`, and raise a meson "ERROR: xxx" in
such a case. However, the code to check for it would raise a python
ValueError if that was the case, so we never got to the properly
formatted error.
D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
Eli Schwartz
Jussi Pakkanen
Dylan Baker
Hemmo Nieminen