[CHERIoT] Enable -Wcheri-compartment-return-void by default

Author: resistor

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2340,13 +2340,11 @@ def note_var_fixit_add_initialization : Note<
   "initialize the variable %0 to silence this warning">;
 def warn_cheri_compartment_void_return_type : Warning <
   "void return on a cross-compartment call makes it impossible for callers to detect failure">,
-  InGroup<CHERICompartmentReturnVoid>,
-  DefaultIgnore;
+  InGroup<CHERICompartmentReturnVoid>;
 def note_cheri_compartment_void_return_type : Note<"replace void return type with int">;
 def warn_cheri_compartment_return_void_or_falloff : Warning <
   "cross-compartement calls that always succeed should return 0 instead">,
-  InGroup<CHERICompartmentReturnVoid>,
-  DefaultIgnore;
+  InGroup<CHERICompartmentReturnVoid>;
 def note_uninit_fixit_remove_cond : Note<
   "remove the %select{'%1' if its condition|condition if it}0 "
   "is always %select{false|true}2">;