add probe-stack support to Julia

[vtjnash]

Looks like support for the "probe-stack" attribute finally landed in LLVM (https://reviews.llvm.org/D34386) thanks to the Rust folks (rust-lang/rust#16012). We should start setting this function attribute in Julia too.

[fisiognomico]

It should not be so hard, as now Julia uses LLVM 6.0.0 it is just needed to add a pass on codegen.
The problem is that looking at Rust stack probes are incompatible with address sanitizer, so maybe it would be wiser to wait that #27167 gets merged, as maybe we can get similar problems in the future for MSAN or TSAN.

[vchuravy]

so maybe it would be wiser to wait that #27167 gets merged, as maybe we can get similar problems in the future for MSAN or TSAN

Best not to block work on the TSAN support, we only need a way to disable probe-stack when sanitizers are used and I can rebase that PR later.

[fisiognomico]

Yeah we can think about that later. Also it seems that the issue is present only with Address Sanitizer, the others are unaffected. I will test it later!

[eulerkochy]

@vtjnash I'm interested to work on this issue. Can you please give me a headstart about the problems and different reading materials?