OSX Tiger: Fix icon

OSX Tiger can only handle `icns` files with up to 256x256 icons.

Adds a file with 256x256, 128x128, 48x48, 32x32, and 16x16 icons.

CMakeLists.txt

@@ -382,7 +382,6 @@ include(functions/set_relative_file_macro)
 set_relative_file_macro(${BIN_TARGET})
 
 if(APPLE)
-  set_source_files_properties("./Packaging/apple/AppIcon.icns" PROPERTIES MACOSX_PACKAGE_LOCATION Resources)
   set(MACOSX_BUNDLE_GUI_IDENTIFIER com.diasurgical.devilutionx)
   set(MACOSX_BUNDLE_COPYRIGHT Unlicense)
   set(MACOSX_BUNDLE_BUNDLE_NAME devilutionx)
@@ -399,7 +398,14 @@ if(APPLE)
     set(MACOSX_BUNDLE_REQUIRED_PLATFORM Carbon)
     set(CMAKE_OSX_DEPLOYMENT_TARGET "10.12.0")
   endif()
-  set_target_properties(${BIN_TARGET} PROPERTIES MACOSX_BUNDLE_ICON_FILE "AppIcon.icns")
+  if(DARWIN_MAJOR_VERSION VERSION_LESS 9)
+    # OSX Tiger can only handle icns files with up to 256x256 icons.
+    set_source_files_properties("./Packaging/apple/AppIcon_256.icns" PROPERTIES MACOSX_PACKAGE_LOCATION Resources)
+    set_target_properties(${BIN_TARGET} PROPERTIES MACOSX_BUNDLE_ICON_FILE "AppIcon_256.icns")
+  else()
+    set_source_files_properties("./Packaging/apple/AppIcon.icns" PROPERTIES MACOSX_PACKAGE_LOCATION Resources)
+    set_target_properties(${BIN_TARGET} PROPERTIES MACOSX_BUNDLE_ICON_FILE "AppIcon.icns")
+  endif()
   set_target_properties(${BIN_TARGET} PROPERTIES MACOSX_BUNDLE_INFO_PLIST "${CMAKE_CURRENT_SOURCE_DIR}/Packaging/apple/Info.plist")
 
   install (TARGETS ${BIN_TARGET} DESTINATION ./)