Access Denied Error when x.py tries to rebuild bootstrap

[Teapot4195]

It appears that x is creating the build folder with the incorrect permissions.

Steps to reproduce

• Clean install.
• Run ./x.ps1 build
• Run any command (like ./x.py test tidy) that rebuilds anything that's already been built using the other shell.
• Observe the following error

error: failed to remove file `C:/msys64/home/siyua/rust/build/bootstrap\debug\rustc.exe`

Caused by:
  Access is denied. (os error 5)
warning: build failed, waiting for other jobs to finish...
error: failed to remove file `C:/msys64/home/siyua/rust/build/bootstrap\debug\bootstrap.exe`

Caused by:
  Access is denied. (os error 5)
failed to run: C:/msys64/home/siyua/rust/build/x86_64-pc-windows-gnu/stage0/bin/cargo.exe build --manifest-path C:/msys64/home/siyua/rust/src/bootstrap/Cargo.toml

Workaround

Navigate to the rust build folder, open properties, navigate to the security tab and make sure that the Users section has permissions for Modify

Head is at ef03fda339923e659d3d3ca3321de887316d2807.

[jyn514]

heh, this is exactly what @Mark-Simulacrum was worried about in #98373 - cargo is trying to recreate the bootstrap.exe file while another instance of bootstrap is running, because we only lock the build directory in the rust process, not in python.

I don't think PowerShell vs python is related, but MSys2 might be setting some environment variable that causes cargo to rebuild, which would explain why no one else has run into this yet.

[Teapot4195]

Oddly I haven't been able to recreate it when it was built by the same shell, but it could just be me.

Edit: Or it could be that I have stumbled into two completely unrelated bugs happening at the same time.