Linux release binaries and object files not stripped

Build QtBase from sources using Qt5.6 and Qt5.8.0-beta.

Steps to reproduce:
1. run configure with options: '-plugin-sql-mysql -plugin-sql-psql -plugin-sql-sqlite -qt-libjpeg -qt-libpng -qt-xcb -no-libudev -sysconfdir /etc/xdg -qt-pcre -R . -openssl -opensource -confirm-license -nomake tests -verbose -prefix work/install -release -force-debug-info -separate-debug-info -nomake examples -no-use-gold-linker'
2. make
3. make install

Separate .debug files are created. Non-debug library files and binaries are shown to be not stripped when running 'file' command for the file.