charts: Follow Qt's already-existent -developer-build option. This means that rebuilding the entirety of Qt with -developer-build will get us all autotests. Furthermore, it fixes the situation on OS X where a debug_and_release build wouldn't actually fully link. In addition, we clean up the tests that were stubbed when internals aren't available to just not build/run them at all by checking private_tests. Change-Id: I5701559cd91df842f78346d7d6ad9295bee587d0 Reviewed-by: Miikka Heikkinen <miikka.heikkinen@theqtcompany.com>