Teach Perl Makefile to build Build for every target

Teach Perl Makefile to build Build for every target

With the previous Perl Makefile.am, running "make check" before
running "make all" would fail on the Perl directory because it
assumed that Build would have been created from Build.PL. Factoring out
the build of Build from Build.PL and making that a prereq of the
pertinent targets avoids that problem on a clean checkout of the
OpenSRF source.

Signed-off-by: Dan Scott <dan@coffeecode.net>