tools_webrtc dir converted to py3 + top level PRESUBMIT script

Bug: webrtc:13607
Change-Id: Ib018e43ea977cc24dd71048e68e3343741f7f31b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/249083
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Jeremy Leconte <jleconte@google.com>
Commit-Queue: Christoffer Jansson <jansson@google.com>
Cr-Commit-Position: refs/heads/main@{#35953}
diff --git a/tools_webrtc/binary_version_check.py b/tools_webrtc/binary_version_check.py
index cc5d961..563fe36 100644
--- a/tools_webrtc/binary_version_check.py
+++ b/tools_webrtc/binary_version_check.py
@@ -1,3 +1,5 @@
+#!/usr/bin/env vpython3
+
 # Copyright (c) 2020 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
@@ -16,19 +18,19 @@
 
 
 if __name__ == '__main__':
-    args = sys.argv
-    if len(args) != 2:
-        print('Usage: binary_version_test.py <FILE_NAME>')
-        exit(1)
-    filename = sys.argv[1]
-    output = subprocess.check_output(['strings', filename])
-    strings_in_binary = output.decode('utf-8').splitlines()
-    for symbol in strings_in_binary:
-        if WEBRTC_VERSION_RE.match(symbol):
-            with open('webrtc_binary_version_check', 'w') as f:
-                f.write(symbol)
-            exit(0)
-    print('WebRTC source timestamp not found in "%s"' % filename)
-    print('Check why "kSourceTimestamp" from call/version.cc is not linked '
-          '(or why it has been optimized away by the compiler/linker)')
-    exit(1)
+  args = sys.argv
+  if len(args) != 2:
+    print('Usage: binary_version_test.py <FILE_NAME>')
+    sys.exit(1)
+  filename = sys.argv[1]
+  output = subprocess.check_output(['strings', filename])
+  strings_in_binary = output.decode('utf-8').splitlines()
+  for symbol in strings_in_binary:
+    if WEBRTC_VERSION_RE.match(symbol):
+      with open('webrtc_binary_version_check', 'w') as f:
+        f.write(symbol)
+      sys.exit(0)
+  print('WebRTC source timestamp not found in "%s"' % filename)
+  print('Check why "kSourceTimestamp" from call/version.cc is not linked '
+        '(or why it has been optimized away by the compiler/linker)')
+  sys.exit(1)