nativesdk-qtbase: make it possible to keep additional libraries

nativesdk-qtbase: make it possible to keep additional libraries

In some usecases for the nativesdk, you might need some build tools that are built upon Qt5. This means
that we're having a need to keep more of the libraries build by nativsdk-qtbase. This patch adds the
infrastructure to support that

(From meta-qt5 rev: b62bda97802a3c79586e4e1c7b31f95e617cc0c8)

Signed-off-by: Anders Darander <anders@chargestorm.se>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>