Fix issue with extra flags

direct/src/showbase/CMakeLists.txt

@@ -4,11 +4,12 @@ set(P3SHOWBASE_FILES
 set(P3SHOWBASE_EXTRA_ARGS "")
 if(IS_OSX) 
   list(APPEND P3SHOWBASE_FILES showBase_assist.mm)
-  set(P3SHOWBASE_EXTRA_ARGS "-ObjC++")
 endif()
 
 add_component_library(p3showbase SYMBOL BUILDING_DIRECT_SHOWBASE ${P3SHOWBASE_FILES})
-set_target_properties(p3showbase PROPERTIES COMPILE_FLAGS ${P3SHOWBASE_EXTRA_ARGS})
+if(APPLE)
+  set_target_properties(p3showbase PROPERTIES COMPILE_FLAGS "-ObjC++")
+endif()
 target_link_libraries(p3showbase p3directbase panda)
 target_interrogate(p3showbase ALL)
 

dtool/src/dtoolutil/CMakeLists.txt

@@ -29,7 +29,6 @@ set(P3DTOOLUTIL_HEADERS
 if(APPLE)
   set(P3DTOOLUTIL_HEADERS ${P3DTOOLUTIL_HEADERS}
     filename_assist.mm filename_assist.h)
-  set(P3DTOOLUTIL_EXTRA_FLAGS "-ObjC++")
   set_source_files_properties(filename_assist.mm filename_assist.h PROPERTIES WRAP_EXCLUDE YES)
 endif()
 
@@ -68,7 +67,6 @@ composite_sources(p3dtoolutil P3DTOOLUTIL_SOURCES)
 
 add_component_library(p3dtoolutil SYMBOL BUILDING_DTOOL_DTOOLUTIL
   ${P3DTOOLUTIL_HEADERS} ${P3DTOOLUTIL_SOURCES})
-set_target_properties(p3dtoolutil PROPERTIES COMPILE_FLAGS ${P3DTOOLUTIL_EXTRA_FLAGS})
 # The extensions need py_panda.h and extension.h from interrogatedb
 target_include_directories(p3dtoolutil PUBLIC
   $<TARGET_PROPERTY:p3interrogatedb,INTERFACE_INCLUDE_DIRECTORIES>)
@@ -76,6 +74,7 @@ target_link_libraries(p3dtoolutil p3dtoolbase ${CMAKE_DL_LIBS})
 target_interrogate(p3dtoolutil ALL EXTENSIONS ${P3DTOOLUTIL_IGATEEXT})
 
 if(APPLE)
+  set_target_properties(p3dtoolutil PROPERTIES COMPILE_FLAGS "-ObjC++")
   find_library(FOUNDATION_LIBRARY Foundation)
   find_library(APPKIT_LIBRARY AppKit)
   target_link_libraries(p3dtoolutil ${FOUNDATION_LIBRARY} ${APPKIT_LIBRARY})