go/internal/gcimporter: fix TestImportStdLib

The test attempted to find all stdlib packages by scanning
pkg/$GOOS_$GOARCH for .a files and then tried to import all of them.
Now that .a files are no longer being placed there, the test is a
noop. Fix this by using go list std (and filtering out testonly
packages) and trying to import all of those to recreate what the test
intended to do.

This also removes a dependency on the pkg/$GOOS_$GOARCH directory
which will stop being produced by dist in CL 453496.

For #47257

Change-Id: I7c1944a89db9da9269def3d64a11408a60d73d46
Reviewed-on: https://go-review.googlesource.com/c/go/+/453858
Reviewed-by: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

0 files changed, 0 insertions, 0 deletions