kbuild: rust: add `CONFIG_RUSTC_VERSION`

Now that we support several Rust versions, introduce
`CONFIG_RUSTC_VERSION` so that it can be used in Kconfig to enable and
disable configuration options based on the `rustc` version.

The approach taken resembles `pahole`'s -- see commit 613fe1692377
("kbuild: Add CONFIG_PAHOLE_VERSION"), i.e. a simple version parsing
without trying to identify several kinds of compilers, since so far
there is only one (`rustc`).

However, unlike `pahole`'s, we also print a zero if executing failed for
any reason, rather than checking if the command is found and executable
(which still leaves things like a file that exists and is executable,
but e.g. is built for another platform [1]). An equivalent approach to
the one here was also submitted for `pahole` [2].

Link: https://lore.kernel.org/rust-for-linux/CANiq72=4vX_tJMJLE6e+bg7ZECHkS-AQpm8GBzuK75G1EB7+Nw@mail.gmail.com/ [1]
Link: https://lore.kernel.org/linux-kbuild/[email protected]/ [2]
Reviewed-by: Nicolas Schier <[email protected]>
Tested-by: Alice Ryhl <[email protected]>
Acked-by: Masahiro Yamada <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>

0 files changed, 0 insertions, 0 deletions