These are necessary for projects outside Meson itself that want to
extend the 'meson install' functionality as meson-python does to
assemble Python package wheels from Meson projects.
Fixes#11426.
It was only trying to guess install tag, and log missing tags, for files
installed by install_data(). Do it also for all other files, especially
custom_taget() that commonly installs generated headers.
There are a couple issues that combine to make the current handling a
bit confusing.
- we call it "install_dir_name" but it is only ever the class default
- CustomTarget always has it set to None, and then we check if it is
None then create a different variable with a safe fallback. The if is
useless -- it cannot fail, but if it did we'd get an undefined
variable error when we tried to use `dir_name`
Remove the special handling for CustomTarget. Instead, just always
accept None as a possible value of outdir_name when constructing install
data, and, if it is None, fall back to {prefix}/outdir regardless of
what type it used to be.
Jussi Pakkanen
Daniele Nicolodi
Xavier Claessens
Eli Schwartz
Filipe Laíns