Tests: Avoid duplicate custom commands for Xcode "new build system"

Tests/CustomCommand/CMakeLists.txt

@@ -514,6 +514,14 @@ add_custom_target(UseConsoleTarget ALL
   USES_TERMINAL
 )
 
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  # Xcode's "new build system" does not support multiple targets
+  # producing the same custom command output.
+  add_custom_target(GenPath DEPENDS "${gen_path}")
+  add_dependencies(NormDepends GenPath)
+  add_dependencies(UseConsole GenPath)
+endif()
+
 # Test COMMAND_EXPAND_LISTS
 set(cmp_args "1ARG=COMMAND_EXPAND_LISTS" "2ARG=test" "3ARG=outfile"
   "4ARG=content")

Tests/Module/ExternalData/Data5/CMakeLists.txt

@@ -6,6 +6,13 @@ ExternalData_Add_Test(Data5.A
     -P ${CMAKE_CURRENT_SOURCE_DIR}/Data5Check.cmake
   )
 ExternalData_Add_Target(Data5.A)
+
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  # Xcode's "new build system" does not support multiple targets
+  # producing the same custom command output.
+  return()
+endif()
+
 ExternalData_Add_Test(Data5.B
   NAME Data5Check.B
   COMMAND ${CMAKE_COMMAND}