add support for escaping for zip2zip

Change-Id: I6c2f39e24247752de065fd3116f670639322b943
Bug: 270896651
Test: zip2zip tests

cmd/zip2zip/zip2zip_test.go

@@ -38,13 +38,6 @@ var testCases = []struct {
 	storedFiles []string
 	err         error
 }{
-	{
-		name: "unsupported \\",
-
-		args: []string{"a\\b:b"},
-
-		err: fmt.Errorf("\\ characters are not currently supported"),
-	},
 	{ // This is modelled after the update package build rules in build/make/core/Makefile
 		name: "filter globs",
 
@@ -406,6 +399,13 @@ var testCases = []struct {
 			"b/a/b",
 		},
 	},
+	{
+		name: "escaping",
+
+		inputFiles:  []string{"a"},
+		args:        []string{"\\a"},
+		outputFiles: []string{"a"},
+	},
 }
 
 func errorString(e error) string {