cmd/dist: add package . to 'go test' commands

cmd/dist: add package . to 'go test' commands

This suppresses verbose output if the test passes,
eliminating some "hello from C" noise for the ../misc/cgo test.

Change-Id: I6324bfb4b3633c20e0eb0ae03aa25d40fab9fcfb
Reviewed-on: https://go-review.googlesource.com/c/go/+/412776
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>