wasm: QOpenGLWidget: ensure depth write is enabled when calling paintGL

Task-number: QTBUG-111304
Pick-to: 6.5 6.4
Change-Id: Ibe9f886b12c89fad7431b77b55c259b15d83559b
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/openglwidgets/qopenglwidget.cpp

@@ -963,6 +963,10 @@ void QOpenGLWidgetPrivate::render()
     f->glViewport(0, 0, q->width() * q->devicePixelRatio(), q->height() * q->devicePixelRatio());
     inPaintGL = true;
 
+#ifdef Q_OS_WASM
+    f->glDepthMask(GL_TRUE);
+#endif
+
     QOpenGLContextPrivate::get(ctx)->defaultFboRedirect = fbos[currentTargetBuffer]->handle();
     q->paintGL();