[Build] (Linux): alias libGL.so and libGL.so.1 to libMobileGL

GLX clients link against libGL; give the Linux build the same alias
treatment libEGL already had so glvnd-less clients can load MobileGL.

CMakeLists.txt

@@ -832,7 +832,7 @@ target_compile_definitions(${CMAKE_PROJECT_NAME}
 
 if(UNIX AND NOT APPLE AND NOT ANDROID)
     foreach(MOBILEGL_LOADER_ALIAS
-            libEGL.so libEGL.so.1)
+            libEGL.so libEGL.so.1 libGL.so libGL.so.1)
         add_custom_command(TARGET ${CMAKE_PROJECT_NAME} POST_BUILD
             COMMAND ${CMAKE_COMMAND} -E create_symlink
                     "$<TARGET_FILE_NAME:${CMAKE_PROJECT_NAME}>"