go.mod: upgrade to go 1.17

This change was produced using 'go mod tidy -go=1.17'
with a go command built at CL 315210.

This activates lazy loading, and updates the go.mod file to maintain
the lazy-loading invariants (namely, including an explicit requirement
for every package transitively imported by the main module).

Note that this does *not* prevent users with earlier go versions from
successfully building packages from this module.

(This has little to no effect for the sys module today because it does
not itself have any module dependencies.)

For golang/go#36460.

Change-Id: I0d278e13e54f961a42cd890ee248ddef811f1a1c
Reviewed-on: https://go-review.googlesource.com/c/sys/+/316111
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
diff --git a/go.mod b/go.mod
index b12171f..29eb4d2 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module golang.org/x/sys
-go 1.12
+go 1.17