Fix OpenGL warnings generated due to CMake deprecations

cmake/sites/Docker-Ubuntu-18_04.cmake

@@ -22,6 +22,8 @@ if("$ENV{RENDERING}" STREQUAL "egl")
   set(EGL_gldispatch_LIBRARY "/usr/lib/x86_64-linux-gnu/libGLdispatch.so" CACHE FILEPATH "")
   set(EGL_opengl_LIBRARY "/usr/lib/x86_64-linux-gnu/libOpenGL.so" CACHE FILEPATH "")
 
+  set(PARAVIEW_EXTRA_CMAKE_ARGUMENTS "-DOpenGL_GL_PREFERENCE:STRING=GLVND" CACHE STRING "")
+
   # If we're going to have support for EGL, index would be nice too
   set(ENABLE_nvidiaindex OFF CACHE BOOL "")
 else()

projects/unix/egl.system.cmake

@@ -7,6 +7,6 @@ superbuild_add_extra_cmake_args(
   -DEGL_LIBRARY:FILEPATH=${EGL_LIBRARY}
   -DEGL_gldispatch_LIBRARY:FILEPATH=${EGL_gldispatch_LIBRARY}
   -DEGL_opengl_LIBRARY:FILEPATH=${EGL_opengl_LIBRARY}
-  -DVTK_USE_OFFSCREEN_EGL:BOOL=ON
+  -DVTK_OPENGL_HAS_EGL:BOOL=ON
   -DVTK_USE_OFFSCREEN:BOOL=OFF
   -DVTK_USE_X:BOOL=OFF)