component/perl: fix post-make-hook

we always had the following warning:

INFO WARNING - several libperl.a found, taking only the first one: /srv/slapgrid/slappart71/srv/runner/shared/perl/aa50bea02bee72b0d400aaaa07ffd490/lib/5.28.1/x86_64-linux-thread-multi/CORE/libperl.a
INFO /srv/slapgrid/slappart71/srv/runner/shared/perl/aa50bea02bee72b0d400aaaa07ffd490/.build/perl-5.28.1/libperl.a
INFO Created symlink "libs-c" to lib/5.28.1/x86_64-linux-thread-multi/CORE

Depending on the order of the list, the link could point to broken
".build" path.