unix: Added linux/sparc64 gccgo support

Change-Id: Iff763334a2efbd44af68048d1de700af7d271647
Reviewed-on: https://go-review.googlesource.com/30755
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/gccgo_linux_sparc64.go

@@ -0,0 +1,20 @@
+// 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.
+
+// +build gccgo,linux,sparc64
+
+package unix
+
+import "syscall"
+
+//extern sysconf
+func realSysconf(name int) int64
+
+func sysconf(name int) (n int64, err syscall.Errno) {
+	r := realSysconf(name)
+	if r < 0 {
+		return 0, syscall.GetErrno()
+	}
+	return r, 0
+}