[compiler-rt] Windows report output options

Devs,

I’m about to start some work to fix some Windows issues for 9.0.0, and I’d like to gather input before I start. I would like to add an option to dump output to a debugger via OutputDebugString along with stdout/stderr. A later addition to this could be an option to output sanitizer reports as Windows events. It seems like there is a similar feature for outputting to syslog for OSX and Android, I would probably take a similar approach.

Are there any objections/suggestions?

-Matthew McGovern

Hi! I work on Mozilla's Windows builds and would be interested in
following along with your progress.

The OutputDebugString sounds like it would be useful in my work. I
don't personally have a use case for the event logging, but I don't
have any particular objection, either.

Something on my wish-list that I've been meaning to write a patch for
but never found time, is the ability to turn off
sys::PrintStackTraceOnErrorSignal completely, and let Windows pass
exceptions to my default postmortem debugger. (I see that there's an
LLVM_DISABLE_CRASH_REPORT variable, but it looks like it would still
exit the app upon an exception, which makes it hard to sprinkle
__debugbreak()'s around for local investigations.)