Update LLVM submodule to include lld NOLOAD fix

[arcnmx]

Rust nightly 2020-05-22 and later ships lld with a regression related to linker scripts: NOLOAD sections incorrectly generate sections filled with 0s. This causes gdb and other elf loaders to write to reserved or otherwise invalid addresses (gdb also seems confused by the resulting ELF files and spits out a warning about the sections). This is particularly a problem for embedded rust projects that use lld by default and have affected linker scripts (cortex-m-rt based projects for instance).

rust-lang/llvm-project#64

Note that this also pulls in llvm changes from #72937

[rust-highfive]

r? @cuviper

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[rust-highfive]

⚠️ Warning ⚠️

• These commits modify submodules.

[nikic]

@bors r+ rollup=never

[bors]

📌 Commit aa7e771 has been approved by nikic

[Dylan-DPC-zz]

@bors p=1

[bors]

⌛ Testing commit aa7e771 with merge a2fc33e...

[bors]

☀️ Test successful - checks-azure
Approved by: nikic
Pushing a2fc33e to master...

[nikic]

Perf changes for reference: https://perf.rust-lang.org/compare.html?start=450abe80f193ccefbfcd48214d70520f2d507f0e&end=a2fc33e0c87a258542cd12d6ffae52c43aa3785a&stat=instructions:u There's a 1% regression for debug builds.

This is expected from the LVI changes this also pulls in. To mitigate, we can backport https://reviews.llvm.org/D80964 once it's ready.