Fix static builds

Disable WebKit2 since WTF from qtdeclarative conflicts with ours,
and renable use of thin archives for static builds, except only use
it for the intermediate staticlibs.

Change-Id: Iee625c5d25f01d1700d4c89028578e4d1288e2ba
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>