tools/test-all.sh: Reimplement in golang

Makes future development easier.

New features:
* A more compact and cleaner results view
* Concurrent testing, much quicker across multiple cores
* Supports comparing output against an expected file, including a text diff of differences. Also has a flag for updating the expected outputs
* Advanced file-globbing support, including scanning for files in subdirectories
* Skip lists are now no longer hidden away in the tool, but defined as a SKIP header in the *.expected.* file

Change-Id: I4fac80bb084a720ec9a307b4acf9f73792973a1d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50903
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>

tools/src/fileutils/fileutils.go

@@ -0,0 +1,29 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package fileutils contains utility functions for files
+package fileutils
+
+import (
+	"os"
+)
+
+// IsExe returns true if the file at path is an executable
+func IsExe(path string) bool {
+	s, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+	return s.Mode()&0100 != 0
+}