android: don't unconditionally use execinfo.h
android: don't unconditionally use execinfo.h

android (a superset or subset, depending on your POV) of Linux doesn't seem to
have execinfo.h, so disable it there.

also simplify the conditional a little so we don't have to alter this all over
the place if the platform support changes in the future.

Change-Id: I937b04f363dfff2b10e1696f11e67d4ba55b3b06
Reviewed-by: Girish Ramakrishnan <c1a9b8418868cd1f28113d279aa10c47940103d8@nokia.com>
Reviewed-by: Gunnar Sletta <d0b71651f3efaa9fda200bbcc395b7b82a871fdd@nokia.com>

qmlc/qtdeclarative,jfaust/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,jfaust/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,crobertd/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,qmlc/qtdeclarative,crobertd/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,jfaust/qtdeclarative,jfaust/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,crobertd/qtdeclarative,corngood/qtdeclarative,corngood/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d