[BUG] Action breaks something in Windows/mingw powershell environment

[WardBrian]

Describe the bug

When using setup-julia, a make command starts to fail on windows-2025 runners.
The same command succeeds when using install-juliaup or not installing julia at all.

On julia 1.10, this just fails, while on julia 1.12, it also leads to a deadhang inside Julia.

To Reproduce

https://github.com/WardBrian/julia-win-dbg/blob/main/.github/workflows/main.yml

Expected behavior

I would not expect installing julia to affect gcc/make's behavior

Screenshots/Build logs

https://github.com/WardBrian/julia-win-dbg/actions/runs/18722648137 (debug logging enabled)

Interesting cases are (windows-latest, lts, pwsh, yes), which uses this action and the command fails, and
(windows-latest, 1.12, pwsh, yes), which uses this action and hangs.

The matrix options are os [windows-latest, windows-2022], version [lts, 1.12], shell [pwsh, bash], and "should I install julia" [yes, no, juliaup]. Besides the two combinations mentioned above, all others succeed.

Additional information

See JuliaLang/julia#59931 for original report.

[WardBrian]

Additional note: There have been other reported issues with gcc in the windows-latest runner (actions/runner-images#13191)

Unsure if these are related, since the build succeeds if setup-julia is not run or if if install-juliaup is used instead.