qt: disable static build for qt-zlib

Static build of applications using qt-zlib and zlib (such as mpv) will
fail because zlib and qt-zlib defines the same functions (inflateReset,
inflatePrime ...)

So add a dependency on !BR2_STATIC_LIBS on BR2_PACKAGE_QT_QTZLIB

Fixes:
 - http://autobuild.buildroot.org/results/0be6e359d46a8a701006305c32b514687854b035



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>