Fix usr-move workaround in the presence of multi-arch.

The cmake directory may not be $PREFIX/lib/cmake, but
instead $PREFIX/lib/<arch>/cmake. Getting the PATH of such a
directory will not lead us to $PREFIX/, but to $PREFIX/lib.

Use a relative calculation instead.

Task-number: QTBUG-33223

Change-Id: Ice4e0f859ab1df238bad4eb942f073e84dd86cc3
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Compile in strict-iterator mode under MSVC

MSVC doesn't like operator->() returning a pointer to
non-aggregate. So we must make sure that the expanded code does not
try to call it by doing:
  abegin->~T();

Instead, we make an implicit call to operator T*() with that
static_cast<T* >. If abegin is a non-strict iterator, it's already
a T*, so the static_cast is a no-op.

qvector.h(645) : error C2839: invalid return type 'int *' for overloaded 'operator ->'

Change-Id: I06f983bab7677cb60ef3913cdce349e26896bfb6
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>