Uninstall MinGW and MSYS on Windows builders to reclaim disk space

[aneeshusa]

servo/servo#16487 automatically cleans out old MSVC rustc and cargo nightlies, but we have ~20GB of old MSYS rustc and cargo nightlies on the Windows builders that won't get automatically removed.

@larsbergstrom or @metajack, now that we're not supporting MinGW/MSYS could one of you please uninstall them on the builders and purge out the C:\msys64 folder holding the old nightlies?

[metajack]

Just needs to happen on servo-windows1 and servo-windows2?

[aneeshusa]

Yes, those are the only 2 windows builders AFAIK.

[metajack]

This is done.

[larsbergstrom]

Wait, I thought we're still supporting MinGW/MSYS for Tor builds of Firefox that include Servo? i.e., we wouldn't test or release the bits, but we'd still ensure Servo builds on it.

[aneeshusa]

See also #620, where we stopping running windows-gnu builds on Windows.

[larsbergstrom]

oh, it looks like @metajack decided to go forward with it - I missed that mail to the thread:
#640 (comment)

I'd propose just reinstalling the tools until we can rewrite the script.