Where I work, it is quite normal to link together C code compiled with GCC and Rust code compiled with LLVM, due to how the build system is set up.
As far as I know that disables LTO, but the build system is so complex, and the C code so large, that nobody bothers switching the C side to Clang/LLVM as well.
As far as I know that disables LTO, but the build system is so complex, and the C code so large, that nobody bothers switching the C side to Clang/LLVM as well.