Revert "Add the same flags for the c++ compiler as they are already defined for the c compiler"

The previous commit was unnecessary.
The value of QMAKE_CFLAGS is used for QMAKE_CXXFLAGS as well.
This is done in qcc-base.conf, which is included via
blackberry-armv7le.conf -> qcc-base-qnx-armv7le.conf -> qcc-base-qnx.conf -> qcc-base.conf
Currently, the BlackBerry arm compiler calls show duplicate entries.

This reverts commit 539f90e9719998e57f17086178eeccdf34f19465.

Change-Id: I6e055ce9aafd16e91e15817946b7561bd76ee43e
Reviewed-by: Bernd Weimer <bweimer@blackberry.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>