[orchestrator] Handles symbolic links when extracting cvd-host_package.tar.gz (google#225)

Author: ser-io

frontend/src/host_orchestrator/orchestrator/testdata/foo.tar.gz

@@ -189,6 +189,10 @@ func untar(dst string, src string) error {
 				return err
 			}
 			f.Close()
+		case tar.TypeSymlink:
+			if err := os.Symlink(header.Linkname, target); err != nil {
+				return err
+			}
 		}
 	}
 }

frontend/src/host_orchestrator/orchestrator/userartifacts.go

@@ -190,6 +190,10 @@ func TestUploadCVDHostPackageSucceds(t *testing.T) {
 	if diff := cmp.Diff("foo\n", string(b)); diff != "" {
 		t.Errorf("aritfact content mismatch (-want +got):\n%s", diff)
 	}
+	b, _ = ioutil.ReadFile(am.GetDirPath("foo") + "/foo_dir/link_foo.txt")
+	if diff := cmp.Diff("foo\n", string(b)); diff != "" {
+		t.Errorf("symlink content mismatch (-want +got):\n%s", diff)
+	}
 	if ok, _ := fileExist(am.GetFilePath("foo", "cvd-host_package.tar.gz")); ok {
 		t.Error("cvd-host_package.tar.gz was not cleaned up")
 	}