cmd/compile: stop leaking 'any' type into user package

The new check corresponds to the (etype != TANY || Debug['A'] != 0)
that was lost in golang.org/cl/19936.

Fixes #14652.

Change-Id: Iec3788ff02529b3b0f0d4dd92ec9f3ef20aec849
Reviewed-on: https://go-review.googlesource.com/20271Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/compile/internal/gc/lex.go

@@ -2264,7 +2264,7 @@ func lexinit1() {
 
 func lexfini() {
 	for _, s := range builtinpkg.Syms {
-		if s.Def == nil {
+		if s.Def == nil || (s.Name == "any" && Debug['A'] == 0) {
 			continue
 		}
 		s1 := Lookup(s.Name)

test/fixedbugs/issue14652.go

+// errorcheck
+
+// Copyright 2016 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 p
+
+var x any // ERROR "undefined: any"