kbuild: rust: re-run Kconfig if the version text changes

kbuild: rust: re-run Kconfig if the version text changes

Re-run Kconfig if we detect the Rust compiler has changed via the version
text, like it is done for C.

Unlike C, and unlike `RUSTC_VERSION`, the `RUSTC_VERSION_TEXT` is kept
under `depends on RUST`, since it should not be needed unless `RUST`
is enabled.

Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20240902165535.1101978-3-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>