meson/docs/markdown/snippets/deprecate_build_always.md

Deprecate build_always

Setting build_always to true for a custom target not only marks the target to be always considered out of date, but also adds it to the set of default targets. This option is therefore deprecated and the new option build_always_stale is introduced.

build_always_stale only marks the target to be always considered out of date, but does not add it to the set of default targets. The old behaviour can be achieved by combining build_always_stale with build_by_default.

The documentation has been updated accordingly.