Scalac testCompilation `.check.out` files in Windows have DOS paths and end of lines

[soronpo]

When running testCompilation under Windows the .check.out files have two problems:

1. Lines are ended with "\r\n" instead of just "\n"
2. Quoted relative position paths inside the check files are using dos \ folder separators instead of / unix separators.

Compiler version

Nightly

Expectation

The output check files should match the Unix standard since this is what the dotty CI expects.