cmd/dist: use GOARM=5 for openbsd/arm

OpenBSD/arm only currently supports softfloat, hence make the default GOARM=5.

Change-Id: Ie3e8f457f001b3803d17ad9bc4ab957b2da18c6a
Reviewed-on: https://go-review.googlesource.com/7614Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/dist/util.go

@@ -505,8 +505,9 @@ func xgetgoarm() string {
 		// Conservative default for cross-compilation.
 		return "5"
 	}
-	if goos == "freebsd" {
+	if goos == "freebsd" || goos == "openbsd" {
 		// FreeBSD has broken VFP support.
+		// OpenBSD currently only supports softfloat.
 		return "5"
 	}
 	if goos != "linux" {