Fix crash on Windows when using Cygwin Git

[500-internal-server-error]

PR Description

Fix crash on Windows when using Cygwin Git by running Unix paths through cygpath. I also thought of just doing the path fixup manually but technically cygpath covers a lot of edge cases that a simple/naive path fixup will probably not, so I went with that. On the other hand, mingw-w64-git recently happened, so maybe this patch isn't needed, but I think it would still be nice to support Cygwin git.

Closes:

• lazygit doesn't work from a Cygwin shell prompt. #5101
• Cannot change directory when using MSYS2/Cygwin git.exe on Windows: "The system cannot find the path specified" #5680
• *fs.PathError chdir /f/dev/projects/zynaddsubfx/zasfx-renew: The system cannot find the path specified. #3447
• Crash on Windows #4883

Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
  • e2e tests don't work on Windows
• Text is internationalised (see here)
  • No new user-facing UI text is added
• If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
  • No configs are added
• Docs have been updated if necessary
• You've read through your own file changes for silly mistakes etc