libgo: update x/sys/cpu after gccgo support added

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/234597

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-bc27341f245a5cc54ac7530d037a609db72b677c
+ea58b8491064fbed18a220571a3043c38dccf7c7
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/golang.org/x/sys/cpu/cpu_aix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build aix,ppc64
+// +build aix
 
 package cpu
 

libgo/go/golang.org/x/sys/cpu/syscall_aix_gccgo.go

@@ -0,0 +1,27 @@
+// Copyright 2020 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.
+
+// Recreate a getsystemcfg syscall handler instead of
+// using the one provided by x/sys/unix to avoid having
+// the dependency between them. (See golang.org/issue/32102)
+// Morover, this file will be used during the building of
+// gccgo's libgo and thus must not use a CGo method.
+
+// +build aix
+// +build gccgo
+
+package cpu
+
+import (
+	"syscall"
+)
+
+//extern getsystemcfg
+func gccgoGetsystemcfg(label uint32) (r uint64)
+
+func callgetsystemcfg(label int) (r1 uintptr, e1 syscall.Errno) {
+	r1 = uintptr(gccgoGetsystemcfg(uint32(label)))
+	e1 = syscall.GetErrno()
+	return
+}