Revert "perl: fix startperl configuration option for perl-native"

This reverts commit f2d1523b.

We've reports of a number of failures from this, it causes pod2man to
reference full paths to perl rather than nativeperl from the environment.
I've also seen this issue locally now. Revert until we can find a solution
which works for everyone.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>