Fix disabling of aliasing for all gcc alike compilers

Don't rely on the makespec to contain g++ in its name, instead use
QMAKE_COMPILER, which gets added to CONFIG.

Fixes crashes on QNX.

Change-Id: If8d2a6a7aa9998b311b2ca137af2fa236adecb00
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
Added changes file

Change-Id: Ia8e0ad300b4651746a7741d0482587cbcd2f891c
Reviewed-by: Florian Bruhin <qt-project.org@the-compiler.org>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Merge remote-tracking branch 'origin/5.4.0' into 5.4

Change-Id: I59ea5b32871dba99276a7e3d9fe5ae8c8487a0d3