The app or its dependencies may link against X11's libGL.1.dylib from
XQuarz, to support GLX on macOS. Doing so may place libGL earlier in
the load order than Apple's OpenGL framework, which results in dlsym
picking symbols from libGL when using the RTLD_DEFAULT lookup strategy,
breaking Qt's OpenGL support in various ways:
QOpenGLShaderProgram: could not create shader program
Warning: "" failed to compile!
To fix this we use RTLD_NEXT, which looks up the symbol in
dependency order of the image that called dlsym, rather than
the global load order.
Change-Id: I1ec3055a4ab0bb96566c7e196d301b30785f2dc0
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
9287447a67