Fix #452 installed binary path check on Windows git bash

[elliotwutingfeng]

Closes #452

When installing on Windows via git bash, command -v mob gives a UNIX style path while $target gives a UNIX style path but with a Windows style drive lettering (e.g. "C:/..."), leading to a mismatch.

This patch checks if the system is Windows, and if so, converts the expected path to the same format (Windows style drive lettering, forward slashes) before comparison.

[gregorriegler]

Thank you very much for looking into this issue.
Unfortunately the proposed solution only works if cygwin is installed. We need this to work regardless.

See https://chatgpt.com/share/6702329e-a264-800f-a7cb-706fccee0716

[elliotwutingfeng]

Current iteration requires sed. MINGW64 does not include any string manipulation tools by default. However, install.sh assumes that curl, grep, cut and tr are available, so there is a good chance sed would be available as well.