unix/linux: update Dockerfile to Go 1.17
unix/linux: update Dockerfile to Go 1.17

Change-Id: Ic711a44c7ecf5d0ab5237a910c920f4b76873c57
Reviewed-on: https://go-review.googlesource.com/c/sys/+/342829
Trust: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Matt Layher <76528ff2e917253aa2211f68e4ca60b5b846dcf5@gmail.com>

golang/sys,golang/sys,golang/sys