temporary fix because of alpha, has to be dropped as soon as gcc's bug is fixed.

--- a/src/opengl/opengl.pro
+++ b/src/opengl/opengl.pro
@@ -53,6 +53,7 @@ contains(QT_CONFIG, opengles2) {
                 gl2paintengineex/qpaintengineex_opengl2_p.h
 }
 
+QMAKE_CXXFLAGS_HIDESYMS -= -fvisibility-inlines-hidden
 
 x11 {
     contains(QT_CONFIG, opengles1)|contains(QT_CONFIG, opengles1cl)|contains(QT_CONFIG, opengles2) {