add uninstall target

[Ckath]

Resolves: not having a working make uninstall

so without this, currently, wxwidgets generates some broken and useless uninstall.cmake, this generates the proper uninstall target. as someone was complaining about in #78

• I made sure the code compiles on my machine
• I made sure there are no unnecessary changes in the code
• I made sure the title of the PR reflects the core meaning of the issue you are solving
• I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"
• I have confirmed that my code does not introduce intentional security flaws

[Ckath]

errors on downloading a sccache zip on windows builds? @meguminloli

[sneedcat]

These links expire every 90 days.
Replace the new one from workflow with this new link.

[Ckath]

what about instead doing https://github.com/mozilla/sccache/archive/refs/tags/v0.2.15.zip or is that not new enough,
edit: ah they dont zip them there for the windows msvc release, whatever. I'll just bump with the new nightly link