cmd/dist: simplify exec.Cmd helpers for Go 1.19
When running on Go 1.19, we can further simplify some of the exec.Cmd
helpers due to API improvements. There's not much point in doing this
while the bootstrap is still 1.17, but this will queue up this
simplification in an obvious way for when we next upgrade the
bootstrap toolchain (#54265).
Updates #44505.
Change-Id: I2ebc3d5c584375ec862a1d48138ab134bd9b2366
Reviewed-on: https://go-review.googlesource.com/c/go/+/427958
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>