package/qt5/qt5base: build Qt 5.6 with LibreSSL if present

LibreSSL build is successful with shared linkage, but not default dlopen().

Also adds patch for successful compilation by using -fpermissive.

Signed-off-by: James Grant <jamesg@zaltys.org>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>