rust: allow version 1.63.0 of rustc

All constructs introduced by newer versions of Rust have been removed.

Apart from Debian 12, all other supported Linux distributions have
rustc 1.75.0 or newer.  This means that they only lack c"" literals
and stable offset_of!.

Tested-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed