Revert "Prepare git src with git worktree"

This causes issues when repeatedly building a package using the same
git checkout.  There is also ambiguity of the default checkout when
trying to build from HEAD. See #142 and #143.

This reverts commit 85c421f1cb.

scripts/libmakepkg/source/git.sh.in

@@ -100,7 +100,7 @@ extract_git() {
 			exit 1
 		fi
 		cd_safe "$srcdir"
-	elif ! git -C "$dir" worktree add --force "${srcdir}/${dir##*/}"; then
+	elif ! git clone --origin=origin -s "$dir" "${dir##*/}"; then
 		error "$(gettext "Failure while creating working copy of %s %s repo")" "${repo}" "git"
 		plainerr "$(gettext "Aborting...")"
 		exit 1