[BUGFIX] Invalid Git command under MS Windows

C:\Program Files (x86)\Git\cmd/git.exe

Due to the blank space in the name, this command cannot be run without
proper escaping.

Change-Id: I23700ef2d7f4c7443797e93b8a78fb7da319eacd
Resolves: #57710
Reviewed-on: https://review.typo3.org/29234
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers