[oe] [meta-qt5] backport 2 commits to krogoth

[Pascal Bach]

Hello

I would like to request a backport of the following two fixes to the krogoth branch of meta-qt5

https://github.com/meta-qt5/meta-qt5/commit/0717c65abc24d67887c93b773129156f714d033b
https://github.com/meta-qt5/meta-qt5/commit/05103827d50ec218954dee3866ec40bee9ec59af

These two issues prevent us from building any CMake enabled projects with an optional dependency to Qt5.
Event recipes in meta-openembedded need some hack to work around this issue: https://github.com/openembedded/meta-openembedded/blob/master/meta-oe/recipes-connectivity/thrift/thrift_0.9.3.bb#L12

Since master is already on 5.7 it would help to have these fixes in krogoth where 5.6 is the default.

Regards
Pascal