rust: kbuild: do not export generated KASAN ODR symbols

rust: kbuild: do not export generated KASAN ODR symbols

ASAN generates special synthetic symbols to help check for ODR
violations. These synthetic symbols lack debug information, so
gendwarfksyms emits warnings when processing them. No code should ever
have a dependency on these symbols, so we should not be exporting them,
just like the __cfi symbols.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250122-gendwarfksyms-kasan-rust-v1-1-5ee5658f4fb6@google.com
[ Fixed typo in commit message. Slightly reworded title. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>