Add missing ksym CONFIG_RUST
Building r27563 without this commit will fail due to this ksym
being undefined in the generic config.
Build system: x86/64
Build-tested: x86/64/AMD Cezanne
Run-tested: x86/64/AMD Cezanne
Signed-off-by: John Audia <therealgraysky@proton.me>
Link: https://github.com/openwrt/openwrt/pull/16464
Signed-off-by: Robert Marko <robimarko@gmail.com>
2eb39308c9