Default `meson setup` arguments

[FFY00]

Currently, we default to -Ddebug=false -Doptimization=2. When we did this, see #27, we always meant to add a way to disable it and allow customizing the options. In #167, we added a way to pass arguments to Meson, but we didn't revisit this.

meson-python/mesonpy/__init__.py

Lines 812 to 814 in f9dc18f

	# TODO: Allow configuring these arguments
	'-Ddebug=false',
	'-Doptimization=2',

So, we need to figure out how this should be configured, and if we should actually have different behaviors, for editable builds for eg.

My initial proposal would be to add a tool.meson-python.args.remove-defaults (alternative name suggestions welcome) setting, which would remove the default arguments. This option would be enabled by default on editable builds, and disabled by default on normal builds.

[dnicolodi]

I don't think we need this. Setting aside the minor issue that I think this is an horrible user interface, there is really no need to remove the default settings, the settings can be simply overridden with the user preferred settings: Meson processes the command line arguments in the order they are specified and later options have precedence on earlier ones. For example:

python -m build -Csetup-args=-Ddebug=true -Csetup-args=-Doptimization=0

If anything, I would fix the UX for passing options to Meson. The current one really looks bad to me, starting with the fact that we need to pass a single Meson option to a configuration setting (setup-args) that has a plural name.

I also think meson-python should not have different default settings for normal and editable wheels. It seems unnecessary and it just going to add confusion. I think meson-python should stay as much as possible out of the way in deciding how things are compiled.

[rgommers]

I think I agree with @dnicolodi, we have enough knobs here, and the overrides are even documented now (e.g., https://meson-python.readthedocs.io/en/latest/how-to-guides/meson-args.html#set-the-build-optimization-level-to-3).

Close?

[FFY00]

Yes, though we still need to order the Meson arguments correctly, to allow users to just override the ones they're supposed to. I'll open a new issue to track that.