Revert "Config: added two new options to configure local builds"

The same can be achieved with a local.mk file.

This reverts commit b84c4641acc5e68f2cf289c1f49b7c7bdaf24c32.
Revert "qt5webkit: enable local build support"

This reverts commit fa2170db78b828894fc12ff1bb98ba59a3850965.