Rust fixes for v6.12 (2nd)
Toolchain and infrastructure:
- Fix several issues with the 'rustc-option' macro. It includes a
refactor from Masahiro of three '{cc,rust}-*' macros, which is not
a fix but avoids repeating the same commands (which would be several
lines in the case of 'rustc-option').
- Fix conditions for 'CONFIG_HAVE_CFI_ICALL_NORMALIZE_INTEGERS'. It
includes the addition of 'CONFIG_RUSTC_LLVM_VERSION', which is not a
fix but is needed for the actual fix.
And a trivial grammar fix.