various fixes for naked_asm! implementation

- fix for divergence
- fix error message
- fix another cranelift test
- fix some cranelift things
- don't set the NORETURN option for naked asm
- fix use of naked_asm! in doc comment
- fix use of naked_asm! in run-make test
- use `span_bug` in unreachable branch

compiler/rustc_passes/src/errors.rs

@@ -1190,9 +1190,8 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for NakedFunctionsAsmBlock {
 #[diag(passes_naked_functions_must_naked_asm, code = E0787)]
 pub(crate) struct NakedFunctionsMustNakedAsm {
     #[primary_span]
+    #[label]
     pub span: Span,
-    #[suggestion(code = "naked_asm!", applicability = "machine-applicable")]
-    pub macro_span: Span,
 }
 
 #[derive(Diagnostic)]