Add CMakeLists for panda/metakubs/pandagl. Not yet built.

panda/metalibs/pandagl/CMakeLists.txt

@@ -0,0 +1,7 @@
+if(HAVE_GL)
+  add_definitions(-DBUILDING_PANDAGL)
+  set(PANDAGL_LINK_TARGETS p3glgsg)
+
+  add_library(pandagl pandagl.cxx)
+  target_link_libraries(pandagl ${PANDAGL_LINK_TARGETS})
+endif()