A custom executable RC should have an executable to set up, not
a command. That is more consistent with the other RCs, too.

Change-Id: I7d71f9f93cd8294132a65fadf2e7a8885143c19d
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>