qt5: reduce closure size

First, closure size is reduced by including the static libraries in $out instead
of trying to move them to $dev. The Qt build system cannot handle libraries
being split between different prefixes. Previously, the static libraries were
moved into $dev and the shared libraries were symlinked from $out to $dev to
fool the build system. However, this causes $dev to be retained at
runtime. Instead, we now keep the static libraries in $out. Fortunately, the
static libraries are not very large anyway.

Second, we build with QT_NO_DEBUG defined unless debugging is enabled. This
causes some assertions to be removed; when assertions are included, they pull
paths from $dev into the runtime closure by using the __FILE__ macro. We also
now patch qtbase to remove even more assertions when QT_NO_DEBUG is defined.