This has been committed to the master branch, but is not present in
1.4 and may not make it to 1.4.x. This patch will fail to apply
if and when it does, so we'll know to simply delete it when the
latest stable Go includes the patch.

--- sys_nacl_amd64p32.s	2014-12-11 01:18:12.000000000 +0000
+++ sys_nacl_amd64p32.s.new	2015-01-12 14:58:08.376023852 +0000
@@ -93,13 +93,13 @@
 	MOVL n+8(FP), DX
 	BSWAPL DX
 	MOVL DX, 12(SP)
-	MOVL $1, DI // standard output
+	MOVL fd+0(FP), DI
 	MOVL SP, SI
 	MOVL $16, DX
 	NACL_SYSCALL(SYS_write)
 
 	// Write actual data.
-	MOVL $1, DI // standard output
+	MOVL fd+0(FP), DI
 	MOVL p+4(FP), SI
 	MOVL n+8(FP), DX
 	NACL_SYSCALL(SYS_write)