debug/elf is only needed to determine the endianness of the host
machine, which is easy to do without debug/elf.

Fixes #15180.

Change-Id: I21035ed3884871270765a1ca3b812a5d4890a7ee
Reviewed-on: https://go-review.googlesource.com/21662Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>