CI: Migrate ::set-env -> $GITHUB_ENV

[oprypin]

Fixes #9785

[bcardiff]

@oprypin would you know why windows builds on fork fails? https://github.com/bcardiff/crystal/runs/1333647009?check_suite_focus=true it seems the timeout in my fork due to llvm build, is that expected?

This is not new to this PR, I think my fork just never succeeded on a windows build. Which is unfortunate because I discover missing bits when submitting PRs only.

[oprypin]

@bcardiff The only reasonable explanation I can see is that at some point the environment of GitHub Actions changed so that this build always breaks, but the cache never expired in the main repo so it still appears OK. I have noticed this problem but have not figured out a solution (although I haven't dug deep at all).

[oprypin]

So it's not a timeout and there actually is relevant output.

https://github.com/bcardiff/crystal/runs/1333355667?check_suite_focus=true#step:20:1623

D:\a\crystal\crystal\llvm-src\include\llvm/ADT/SmallVector.h(315,32): error C2976: 'llvm::SmallVectorTemplateBase': too few template arguments (compiling source file D:\a\crystal\crystal\llvm-src\lib\ExecutionEngine\RuntimeDyld\RTDyldMemoryManager.cpp) [D:\a\crystal\crystal\llvm-src\lib\ExecutionEngine\RuntimeDyld\LLVMRuntimeDyld.vcxproj]
D:\a\crystal\crystal\llvm-src\include\llvm/ADT/SmallVector.h(179): message : see declaration of 'llvm::SmallVectorTemplateBase' (compiling source file D:\a\crystal\crystal\llvm-src\lib\ExecutionEngine\RuntimeDyld\RTDyldMemoryManager.cpp) [D:\a\crystal\crystal\llvm-src\lib\ExecutionEngine\RuntimeDyld\LLVMRuntimeDyld.vcxproj]

Must have been a compiler update.

[oprypin]

Tried to bump LLVM minor version, that didn't help
https://github.com/oprypin/crystal/actions/runs/339148829