zip: fix TestCreateFromDirSpecial/ignore_symlink on wasmtime

The wasmtime runtime does not permit absolute symlinks.

More generally: since this is an x-repo, we should not assume anything
in particular about the set of supported operating systems. We should
explicitly list the GOOS values expected to always support symlinks,
rather than the ones that are allowed not to.

Fixes golang/go#60795.

Change-Id: I1749429ac1178f261b4acfd97c0fcf9ec1c2a871
Reviewed-on: https://go-review.googlesource.com/c/mod/+/504075
Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>

zip/zip_test.go

@@ -537,10 +537,11 @@ func TestCreateFromDirSpecial(t *testing.T) {
 			setup: func(t *testing.T, tmpDir string) string {
 				if err := os.Symlink(tmpDir, filepath.Join(tmpDir, "link")); err != nil {
 					switch runtime.GOOS {
-					case "plan9", "windows":
-						t.Skipf("could not create symlink: %v", err)
-					default:
+					case "aix", "android", "darwin", "dragonfly", "freebsd", "illumos", "ios", "js", "linux", "netbsd", "openbsd", "solaris":
+						// Symlinks in tmpDir are always expected to work on these platforms.
 						t.Fatal(err)
+					default:
+						t.Skipf("could not create symlink: %v", err)
 					}
 				}
 				return tmpDir