Support processing minidumps

[EricRahm]

Marionette can use mozcrash to process minidumps in the event of a browser crash and generate a stack trace. To support this we need to specify a path to minidump_stackwalk (this can be downloaded via mozharness) in the MINIDUMP_STACKWALK env var. Additionally we need to provide a symbols location (this can be a URL or a local file), presumably this lives next to the binary on archive.m.o.

[EricRahm]

I guess it's tooltool for getting minidump_stackwalk, from IRC conversation with ted:

09:33 ted: so lets say I just want to get minidump_stackwalk on my test machine, what's a good way to do that?
09:33 <•ted> https://dxr.mozilla.org/mozilla-central/source/testing/mozharness/mozharness/mozilla/testing/testbase.py#672
09:33 <•ted> so that's the code that handles that 'download_minidump_stackwalk' attribute
09:34 <•ted> https://dxr.mozilla.org/mozilla-central/source/testing/config/tooltool-manifests/
09:34 <•ted> the tooltool manifests it uses are under there
09:34 <•ted> like https://dxr.mozilla.org/mozilla-central/source/testing/config/tooltool-manifests/linux64/releng.manifest
09:34 <•ted> what you can do, very simply, is grab https://github.com/mozilla/build-tooltool/raw/master/tooltool.py
09:35 <•ted> then run python tooltool.py -m /path/to/manifest fetch
09:36 <•ted> and that will download the binary to the cwd