[LLVM-158] Monitor and maintain buildbots - Some work to track down a faulty msan test on AArch64 that was intermittently failing. - Spent some time trying to reproduce an intermittent failure in libfuzzer.

[LLVM-523] Synthesise EXIDX_CANTUNWIND entries for sections without tables. - Not getting much response from upstream beyond a vague suggestion to rewrite the whole of .ARM.exidx handling as a single custom section. I may have to go down this path to get the feature accepted, even if it is to show that it is a bad idea.

[LLVM-496] LLD in linux kernel - Submitted patch to ignore -p (--no-pipeline-knowledge) which is used by the AArch32 linux kernel. - Submitted patch to integrate LLD in TCWG kernel regression test. - Learned, the hard way, about how the linux kernel build system works and how to pass extra flags.

Reviews: Spent an awful long time looking at how clang passes options to GNU as to try and match the existing clang defaults. I'm not sure I've seen anything much more confusing than tracing through target features from clang to llvm and back again.