cheri compartment warn void return: fix tests

An explicit flag is now necessary.

Author: v01dxyz

clang/test/Sema/cheri/cheri-compartment-warn-if-return-void-or-unused.c

@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 %s -o - -triple riscv32-unknown-unknown -emit-llvm -mframe-pointer=none -mcmodel=small -target-cpu cheriot -target-feature +xcheri -target-feature -64bit -target-feature -relax -target-feature -xcheri-rvc -target-feature -save-restore -target-abi cheriot -Oz -cheri-compartment=example -verify -fsyntax-only
-// RUN: %clang_cc1 %s -o - -triple riscv32-unknown-unknown -emit-llvm -mframe-pointer=none -mcmodel=small -target-cpu cheriot -target-feature +xcheri -target-feature -64bit -target-feature -relax -target-feature -xcheri-rvc -target-feature -save-restore -target-abi cheriot -Oz -cheri-compartment=example -fdiagnostics-parseable-fixits -fsyntax-only 2>&1 | FileCheck %s
+// RUN: %clang_cc1 %s -o - -triple riscv32-unknown-unknown -emit-llvm -mframe-pointer=none -mcmodel=small -target-cpu cheriot -target-feature +xcheri -target-feature -64bit -target-feature -relax -target-feature -xcheri-rvc -target-feature -save-restore -target-abi cheriot -Oz -cheri-compartment=example -Wcheri-compartment-return-void -verify -fsyntax-only
+// RUN: %clang_cc1 %s -o - -triple riscv32-unknown-unknown -emit-llvm -mframe-pointer=none -mcmodel=small -target-cpu cheriot -target-feature +xcheri -target-feature -64bit -target-feature -relax -target-feature -xcheri-rvc -target-feature -save-restore -target-abi cheriot -Oz -cheri-compartment=example -Wcheri-compartment-return-void -fdiagnostics-parseable-fixits -fsyntax-only 2>&1 | FileCheck %s
 
 __attribute__((cheri_compartment("example"))) void void_return_type_f(int a) // expected-warning{{void return on a cross-compartment call makes it impossible for callers to detect failure}} expected-note{{replace void return type with int}}
 {