libcgo: fix NaCl build.

R=r, rsc, nigeltao
CC=golang-dev
https://golang.org/cl/2110046

src/libcgo/Makefile

@@ -16,9 +16,10 @@ OFILES=\
 HOST_CFLAGS_386=-m32
 HOST_CFLAGS_amd64=-m64
 
-LDFLAGS_linux=-shared -lpthread -lm
 LDFLAGS_darwin=-dynamiclib -Wl,-undefined,dynamic_lookup /usr/lib/libpthread.dylib
-LDFLAGS_freebsd=-pthread -shared -lm
+LDFLAGS_freebsd=-shared -lm -pthread
+LDFLAGS_linux=-shared -lm -lpthread
+LDFLAGS_nacl=-shared -lm -lpthread
 LDFLAGS_windows=-shared -lm -mthreads
 
 %.o: %.c

src/libcgo/nacl_386.c

-/* unimplemented */
+// Copyright 2010 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.
+
+#include "libcgo.h"
+
+void
+initcgo(void)
+{
+}
+
+void
+libcgo_sys_thread_start(ThreadStart *ts)
+{
+	// unimplemented
+	*(int*)0 = 0;
+}

src/pkg/os/dir_nacl.go

@@ -57,7 +57,7 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 				continue
 			}
 			bytes := (*[10000]byte)(unsafe.Pointer(&dirent.Name[0]))
-			var name = string(bytes[0:clen(bytes)])
+			var name = string(bytes[0:clen(bytes[0:])])
 			if name == "." || name == ".." { // Useless names
 				continue
 			}