Update compiler-rt submodule

[ishitatsuyuki]

This brings in LLVM 5 related changes. Not tested.

[ishitatsuyuki]

CI failure due to homebrew failing on outdated Ruby.

[alexcrichton]

I don't think we're ready for LLVM 5 to land upstream in rustc, so why would we land this ahead of time?

[ishitatsuyuki]

There's sanitizer linkage issues; and we're behind the schedule.

[alexcrichton]

That's... not really an answer though? We can't land this until we can upgrade to LLVM 5, right?

[Amanieu]

compiler-rt doesn't depend on LLVM and can be updated independently.

[ishitatsuyuki]

• the current code base has compile issues with glibc 2.26.
• the current code base is incompatible with latest LLVM sanitizers.
• the upgrade should be back compat, but it may cause the sanitizers to fail weird. Needs test.

[alexcrichton]

Aren't the newer sanitizers not guaranteed to be compatible with older LLVM? Are we sure that this upgrade of the compiler-rt submodule actually works with the LLVM rustc is using?

[ishitatsuyuki]

Let's test it. I will open a WIP PR to rust repo tomorrow.

[alexcrichton]

According to rust-lang/rust#45779 sounds like we're not quite ready for this, so closing