gccjit does not build on s390x due to old libc dependency

[uweigand]

Running ./x.py check on s390x fails when attempting to build rustc_codegen_gcc due to:

Checking stage0 gcc artifacts (s390x-unknown-linux-gnu)
    Updating git repository `https://github.com/antoyo/gccjit.rs`
  Downloaded libc v0.1.12
  Downloaded 1 crate (31.1 KB) in 0.42s
    Checking libc v0.1.12
    Checking smallvec v1.10.0
error[E0433]: failed to resolve: could not find `arch` in `os`
   --> /home/uweigand/.cargo/registry/src/github.com-eae4ba8cbf2ce1c7/libc-0.1.12/rust/src/liblibc/lib.rs:100:20
    |
100 | pub use types::os::arch::c95::*;
    |                    ^^^^ could not find `arch` in `os`

This seems to be caused by a dependency on libc 0.1.12 from gccjit_sys. This version is very old (from about 2015), and does not yet support the s390x architecture at all.

@antoyo could this be updated to a more recent libc version? If so, would you like me to send a patch against https://github.com/antoyo/gccjit.rs ?

[antoyo]

@antoyo could this be updated to a more recent libc version? If so, would you like me to send a patch against https://github.com/antoyo/gccjit.rs ?

Yes, please!

[uweigand]

Thanks for the quick merge! I see ./x.py check still fails for now, because the rust build still seems to pull in the eefb8c662d commit of gccjit.rs, probably because of the Cargo.lock in rustc_codegen_gcc.

Will this be pulled forward automatically at some point, or do I need to submit another PR? (If so, against which repo?)

[antoyo]

The fastest would be to update the Cargo.lock in this repo (rust-lang/rust). I would appreciate if you submit a PR for this. Thanks!

[uweigand]

I've updated the gccjit.rs dependency to the current head commit and rebuilt. This automatically removed the libc 0.1 dependency from Cargo.lock; it is now using 0.2.112 (the version that was also already present in Cargo.lock) everywhere, which is fine for s390x.

[uweigand]

With that PR applied, ./x.py check now passes on s390x.