package/netsurf: do not allow on static linking configurations

Static linking does not work properly in netsurf, nobody fixed it, and
the netsurf build system is completely broken. Let's disable the
package for static linking configurations.

Fixes:

  http://autobuild.buildroot.net/results/28b43c29e241080e23c87145797ea00dc4b3970d/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>