qt: Script Module needs a toolchain with NPTL

Qt Script Module uses pthread_getattr_np() which is implemented in
toolchains with NPTL. Otherwise the compilation will fail showing this
error message:

../3rdparty/javascriptcore/JavaScriptCore/runtime/Collector.cpp: In
function ‘void* QTJSC::currentThreadStackBase()’:
../3rdparty/javascriptcore/JavaScriptCore/runtime/Collector.cpp:692:42:
error: ‘pthread_getattr_np’ was not declared in this scope

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>