package qt: stop building static qtwebkit

Static qtwebkit seemed to build successfully, but applications
could not link to it successfully since Qt 4.8.0 (qtbwebkit 2.0).

See https://github.com/mxe/mxe/issues/23

src/qt.mk

@@ -37,7 +37,7 @@ define $(PKG)_BUILD
         -script \
         -no-iconv \
         -opengl desktop \
-        -webkit \
+        -no-webkit \
         -no-glib \
         -no-gstreamer \
         -no-phonon \