go/internal/gcimporter,cmd/compile/internal/importer: skip tests that need 'go list...

go/internal/gcimporter,cmd/compile/internal/importer: skip tests that need 'go list' on js/wasm

js/wasm doesn't support os.Exec, so it can't run 'go list' to locate
export data for packages in the standard library.

This fixes js/wasm test failures introduced in CL 442303.

For #47257.

Change-Id: I39289f376691493aa6fb447b3329f6508ab48d58
Reviewed-on: https://go-review.googlesource.com/c/go/+/444015
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>