syscall: prevent redundant newline from empty $extraimports
Currently mksyscall script produces one redundant newline
when $extraimports is empty, leading to a gofmt warning
reported by "git codereview change".
Change-Id: I57b0fa040347375698973e777285deded16ab62e
Reviewed-on: https://go-review.googlesource.com/c/go/+/587877 Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>