Panic in Windows when running on different mounts

[DanielSchiavini]

Version Information

• vyper Version (output of vyper --version): at least 0.3.4~0.4.0
• OS: windows
• Python Version: 3.11

What's your issue about?

Compiler panics with error "path exists outside base folder".

• This error was encountered in this workflow.
• Apparently the working folder in Github actions is overridden to the D: drive. The Vyper binary and/or the files being compiled are in the C: drive.
• Even if we use the --standard-json input, importing built-in interfaces will raise this error.

For example in Vyper 0.4.0, the standard json input:

{
  "language": "Vyper",
  "settings": {
    "outputSelection": {
      "*": {
        "*": [
          "evm.bytecode.object"
        ]
      }
    }
  },
  "sources": {
    "contracts/Foo.vy": {
      "content": "\nfrom ethereum.ercs import IERC20\n\n@external\ndef foo() -> int128:\n    return 13\n"
    }
  }
}

Results in:

{
  "compiler": "vyper-0.4.0",
  "errors": [
    {
      "component": "compiler",
      "formattedMessage": "unhandled exception path is on mount 'C:', start on mount 'D:'\n\n  contract \"contracts/Foo.vy:2\", line 2:0 \n       1\n  ---> 2 from ethereum.ercs import IERC20\n  -------^\n       3\n\n\nThis is an unhandled internal compiler error. Please create an issue on Github to notify the developers!\nhttps://github.com/vyperlang/vyper/issues/new?template=bug.md",
      "message": "unhandled exception path is on mount 'C:', start on mount 'D:'",
      "severity": "error",
      "sourceLocation": {
        "file": "contracts\\Foo.vy"
      },
      "type": "CompilerPanic"
    }
  ]
}

How can it be fixed?

We probably need to be more careful when using relative paths.