re PR go/86535 (FreeBSD/PowerPC64 - Building Go Frontend support for gcc 7.3.0 fails)

	PR go/86535
    runtime: always declare nanotime in Go
    
    For libgo it's always defined in C.
    
    Updates https://gcc.gnu.org/PR86535
    
    Reviewed-on: https://go-review.googlesource.com/c/163743

From-SVN: r269214

gcc/go/gofrontend/MERGE

-51d2cb40a6475b126ed66cefa2aa6c8dbdc806d0
+e330eea4464f1513808ccd95011edb4ccbe946b5
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/runtime/stubs3.go

@@ -2,13 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !plan9
-// +build !windows
-// +build !nacl
-// +build !freebsd
-// +build !darwin
-// +build !aix
-
 package runtime
 
 func nanotime() int64