This allows us to modify this file and fix it more fluidly. Users can
invoke it from go generate via:
go run golang.org/x/sys/windows/mkwinsyscall
This was taken from Go repo commit 6b85fa80.
Updates golang/go#34388
Change-Id: I8dc39eed96b2499ccbde53554b3e16e6c1f6aa98
Reviewed-on: https://go-review.googlesource.com/c/sys/+/198637
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
