go/packages: replace darwin with netbsd in TestSizes

The darwin/386 port has been removed per golang.org/issue/37610.
TestSizes needs an operating system that has both amd64 and 386 ports,
so darwin no longer qualifies. NetBSD has had its 386 port restored
recently in golang/go#31726, so it can be used instead.

Fixes golang/go#38319.
For golang/go#37610.

Change-Id: I37ce6d86ca3ddad43e9294e0de66f36091cba54a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/227552
Reviewed-by: Benny Siegert <[email protected]>

Author: dmitshur

go/packages/packages_test.go

@@ -1584,12 +1584,12 @@ func testContainsOverlayXTest(t *testing.T, exporter packagestest.Exporter) {
 // This test ensures that the effective GOARCH variable in the
 // application determines the Sizes function used by the type checker.
 // This behavior is a stop-gap until we make the build system's query
-// too report the correct sizes function for the actual configuration.
+// tool report the correct sizes function for the actual configuration.
 func TestSizes(t *testing.T) { packagestest.TestAll(t, testSizes) }
 func testSizes(t *testing.T, exporter packagestest.Exporter) {
 	// Only run this test on operating systems that have both an amd64 and 386 port.
 	switch runtime.GOOS {
-	case "darwin", "linux", "windows", "freebsd", "openbsd", "android":
+	case "linux", "windows", "freebsd", "openbsd", "netbsd", "android":
 	default:
 		t.Skipf("skipping test on %s", runtime.GOOS)
 	}