Disable -Bsymbolic-functions on everything but x86

Causes signal not found errors with C++11 signals on ARM.
qtbase already disables it with a configure check [1] but we did use
it here for frameworks.  See bug report for more information [2].

[1] https://codereview.qt-project.org/#/c/81095/
[2] https://bugreports.qt-project.org/browse/QTBUG-36129