build static qbs lib if static Qt is used

Change-Id: I397c1b830262d62f68de070a2e4777155728139f
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Refactor setting up built-in items.

One function per item for easier maintenance. Fixes some subtle bugs
along the way.

Change-Id: Iab91818ee8111e626ea167470a446f73845163b5
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>