Add STATIC_ASSERT_INCOMPLETE_TYPE to enforce include minimality.

Add enforcements against `Dictionary` for `ustring.h` and two for `Dictionary` and `String` from `array.h`.

SConstruct

@@ -634,6 +634,7 @@ if env["strict_checks"]:
 
 # Run SCU file generation script if in a SCU build.
 if env["scu_build"]:
+    env.Append(CPPDEFINES=["SCU_BUILD_ENABLED"])
     max_includes_per_scu = 8
     if env.dev_build:
         max_includes_per_scu = 1024