cmd/dist: add mips and mipsle as GOARCH values

Change-Id: I7a51d5d96a7cb87c40ade5be276136c465010bb9
Reviewed-on: https://go-review.googlesource.com/32596Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Vladimir Stefanovic <vladimir.stefanovic@imgtec.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/dist/build.go

@@ -57,6 +57,8 @@ var okgoarch = []string{
 	"amd64p32",
 	"arm",
 	"arm64",
+	"mips",
+	"mipsle",
 	"mips64",
 	"mips64le",
 	"ppc64",