build: Do not force a specific perl from ${PERL} when running pod2man

build: Do not force a specific perl from ${PERL} when running pod2man

pod2man should have the right #!/usr/bin/perl line already, and forcing it may
cause us to use the wrong perl.

Essentially treat this like any other system binary, rather than forcing
it to use the first perl we found.

This essentially reverts e80f576db66ad04592ac436ed74ceb9b96452060.
Current SLES11 does not seem to have the issue this was added to
address.

Andrew Bartlett

Reviewed-by: Michael Adam <obnox@samba.org>
Autobuild-User(master): Michael Adam <obnox@samba.org>
Autobuild-Date(master): Thu Feb 28 02:14:25 CET 2013 on sn-devel-104