Review POSITION_INDEPENDENT_CODE use of -fPIE

This issue was created automatically from an original Mantis Issue. Further discussion may take place here.

Original description:

cmLocalGenerator::AddPositionIndependentFlags uses -fPIE for executables and -fPIC for libraries. This caused issues in Qt:

https://bugreports.qt.io/browse/QTBUG-45755

https://codereview.qt-project.org/#/c/112060/

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65886

Someone who understands the terms-of-art used in the discussion should review what cmake is doing here.