test: new testcase for gollvm bug

Testcase for a gollvm bug (assert in Llvm_backend::materializeComposite).

Updates golang/go#33020.

Change-Id: Icdf5b4b2b6eb55a5b48a31a61c41215b1ae4cf01
Reviewed-on: https://go-review.googlesource.com/c/go/+/191743Reviewed-by: Ian Lance Taylor <iant@golang.org>

test/fixedbugs/issue33020a.dir/a.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type FArg func(args []string) error
+
+type Command struct {
+	Name string
+	Arg1 FArg
+	Arg2 func(args []string) error
+}

test/fixedbugs/issue33020a.dir/b.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+var Cmd = &a.Command{
+	Name: "test",
+}
+
+func main() {
+}

test/fixedbugs/issue33020a.go

+// compiledir
+
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 33020: gollvm assert in Llvm_backend::materializeComposite
+
+package ignored