package/zsh: Enable dynamic modules

The autoconf scripts seem to assume that no dynamic loader
is available if crosscompiling.
This results in only a small set of modules being enabled
and linked statically.

For comparison, debian patches the fallback to enable
dynamic modules (unconditionally).

This commit enables modules if shared libraries are enabled.

Signed-off-by: Norbert Lange <nolange79@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>