CMake: Update egg/physics metalibs to add_metalib(... INIT ...)

panda/metalibs/pandaegg/CMakeLists.txt

@@ -2,9 +2,9 @@ if(NOT HAVE_EGG)
   return()
 endif()
 
-set(PANDAEGG_LINK_TARGETS p3egg p3egg2pg)
-
-add_metalib(pandaegg pandaegg.cxx COMPONENTS ${PANDAEGG_LINK_TARGETS})
+add_metalib(pandaegg
+  INIT init_libpandaegg pandaegg.h
+  COMPONENTS p3egg p3egg2pg)
 target_link_libraries(pandaegg panda)
 
 install(TARGETS pandaegg DESTINATION lib)

panda/metalibs/pandaphysics/CMakeLists.txt

@@ -1,3 +1,5 @@
-add_metalib(pandaphysics pandaphysics.cxx COMPONENTS p3physics p3particlesystem)
+add_metalib(pandaphysics
+  INIT init_libpandaphysics pandaphysics.h
+  COMPONENTS p3physics p3particlesystem)
 
 install(TARGETS pandaphysics DESTINATION lib)