Incremental ThinLTO fails for style-servo and script-servo on perf.rlo #53947
Description
The compiler seems to open too many files at once:
thread \'main\' panicked at \'failed to open bitcode file `/tmp/.tmpgMegOo/target/release/incremental/style-1fatvssee0g94/s-f4hlkotafd-18kxxq0-working/51kw0352sas5fu11.pre-thin-lto.bc`: Too many open files (os error 24)\', librustc_codegen_llvm/back/write.rs:2477:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
I don't know yet how to best fix this:
- Either only use memory mapped files up to some limit and load the rest of the files eagerly,
- or generally limit the number of object files we partition a crate into (something people are asking for anyway).