We will still try to load `meson_options.txt` if `meson.options` doesn't
exist. Because there are some advantages to using `meson.options` even
with older versions of meson (such as better text editor handling)
we will not warn about the existence of a `meson.options` file if a
`meson_options.txt` file or symlink also exists.
The name `meson.options` was picked instead of alternative proposals,
such as `meson_options.build` for a couple of reasons:
1. meson.options is shorter
2. While the syntax is the same, only the `option()` function may be
called in meson.options, while, it may not be called in meson.build
3. While the two files share a syntax and elementary types (strings,
arrays, etc), they have different purposes: `meson.build` declares
build targets, `meson.options` declares options. This is similar to
the difference between C's `.c` and `.h` extensions.
As an implementation detail `Interpreter.option_file` has been removed,
as it is used exactly once, in the `project()` call to read the options,
and we can just calculate it there and not store it.
Fixes: #11176
Link to feature options consistently, and point out that it controls
"whether" the function finds what it's trying to find. This clues people
in to the fact that disabled features exist.
This is based on searching for `@FeatureNew*` decorators.
There is also one correction to a version in a decorators;
`build_by_default` was added in #1303, which is 0.38.0, not 0.40.0.
Xavier Claessens
Dylan Baker
Eli Schwartz
Will Thompson
Elliott Sales de Andrade
Daniel Mensinger