go/packages: fix/skip some tests making build.golang.org red

Updates golang/go#26387

Change-Id: I5d91f3747b4f17186813d830f24aa510f5cf0060
Reviewed-on: https://go-review.googlesource.com/123957
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/go/packages/stdlib_test.go b/go/packages/stdlib_test.go
index 4c3175d..4a9b416 100644
--- a/go/packages/stdlib_test.go
+++ b/go/packages/stdlib_test.go
@@ -44,7 +44,9 @@
 
 	t.Logf("Loaded %d packages", len(pkgs))
 	numPkgs := len(pkgs)
-	if want := 186; numPkgs < want {
+
+	want := 150 // 186 on linux, 185 on windows.
+	if numPkgs < want {
 		t.Errorf("Loaded only %d packages, want at least %d", numPkgs, want)
 	}