Support -debug-and-release under Linux

It would be great to have support for debug+release builds of Qt under Linux, and have them shipped as part of the installer.

The debug build would be compiled under QT_DEBUG, all assertions enabled, -Og, debug symbols in separate files (depending on configure's -separate-debug-info)

The release builld would be compiled without QT_DEBUG (... with QT_NO_DEBUG), assertions disabled, -O2 / -O3 as needed; debug symbols would still be produced under -force-debug-info (for profiling) and possibly stored in separate files.

This would actually make the SDK much, much more useful for development on Linux. E.g. with this I would be able to debug into Qt, package, deploy, profile my application; without requiring me building Qt 2-3 times manually, and cope with different kits in Creator.