cmd/dist: build bootstrap toolchain with -l

cmd/dist: build bootstrap toolchain with -l

Workaround Go 1.4 compiler bugs.  See discussion at:
https://groups.google.com/d/msg/golang-dev/Ss7mCKsvk8w/Gsq7VYI0AwAJ

Change-Id: I842335fddffb67a6e21c000fe5bef258ea61c77a
Reviewed-on: https://go-review.googlesource.com/20690
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>