scripts: Allow git user override
scripts: Allow git user override

This is needed for automated building as we do not typically have a
.gitconfig specified.

Signed-off-by: Preetam D'Souza <217a41a8be005ac7f6a1c1c5a42b81b8928ed037@gmail.com>

maruos/mflinger,maruos/mflinger,maruos/mflinger