lighttpd: disable static build

lighttpd modules support code requires shared libraries support.

The scons based build system seems to be support static link of modules, but
we currently don't use scons for lighttpd.

Fixes:
http://autobuild.buildroot.net/results/39c/39c027bf6b76a0f9c15a184f449dadacfaefe980/



[Peter: move to top of file to fix indentation of sub options]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>