[Bugpoint] Do not create illegal function attribute combos

[greened]

Summary

If a function requires optnone to trigger a crash, it must also have noline,
otherwise it will fail a verifier check.

[sebpop]

Looks good to me. Thanks!

llvm/test/BugPoint/attr-crash.ll

+; RUN: bugpoint -load %llvmshlibdir/BugpointPasses%shlibext %s -output-prefix %t -bugpoint-crashfuncattr 2>&1 | FileCheck %s
+; REQUIRES: plugins
+;
+; ModuleID = 'attr-crash.ll'
+source_filename = "test.c"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local i32 @main(i32 %argc, i8** %argv) local_unnamed_addr #0 {
+  ret i32 0
+}
+
+; CHECK-NOT: Attribute 'optnone' requires 'noinline'!
+attributes #0 = { noinline nounwind optnone uwtable "bugpoint-crash" }

llvm/tools/bugpoint/CrashDebugger.cpp

for (auto A : Attrs)
     AB.addAttribute(A);
   AttributeList NewAttrs;
   NewAttrs =
       NewAttrs.addAttributes(BD.getContext(), AttributeList::FunctionIndex, AB);
 
   // Set this new list of attributes on the function.
   F->setAttributes(NewAttrs);
 
+  // If the attribute list includes "optnone" we need to make sure it also
+  // includes "noinline" otherwise we will get a verifier failure.
+  if (F->hasFnAttribute(Attribute::OptimizeNone))
+    F->addFnAttr(Attribute::NoInline);
+
   // Try running on the hacked up program...
   if (TestFn(BD, M.get())) {
     BD.setNewProgram(std::move(M)); // It crashed, keep the trimmed version...
 
     // Pass along the set of attributes that caused the crash.
     Attrs.clear();
     for (Attribute A : NewAttrs.getFnAttributes()) {
       Attrs.push_back(A);