Revert "Don't source script output"

This reverts commit 730c53263f.

install.sh

@@ -26,7 +26,7 @@ read blockdevice
 for check in checks/*.check
 do
 	echo "=> Running check '$check'..."
-	. $check
+	$($check)
 	return=$?
 	if [ "$return" -ne 0 ]; then
 		echo "=> Check failed. Fix it, maybe."
@@ -37,7 +37,7 @@ done
 for step in steps/*.step
 do
 	echo "=> Running step '$step'..."
-	. $step
+	$($step)
 	return=$?
 	if [ "$return" -ne 0 ]; then
 		echo "=> Step failed. That is weird. Sorry. Check logs maybe."