Rust fixes for v6.12 (3nd) Toolchain and infrastructure: - Avoid build errors with old 'rustc's without LLVM patch version (important since it impacts people that do not even enable Rust). - Update LLVM version for 'HAVE_CFI_ICALL_NORMALIZE_INTEGERS' in 'depends on' condition (the fix was eventually backported rather than land in LLVM 19).