fix /bin/sh startup check on non-default sh prompt
fix /bin/sh startup check on non-default sh prompt

... as for example needed on stampede :-P

luis-rr/saga-python,mehdisadeghi/saga-python,luis-rr/saga-python,mehdisadeghi/saga-python,telamonian/saga-python,telamonian/saga-python,luis-rr/saga-python