Update buildtools (gn and clang-format)

This updates buildtools to 8b16338d17cd. gn has migrated out of
buildtools and into its own cipd package, so gn is pulled at
2ecd43a10266 (current). This provides a mac-x86_64 or mac-arm64 gn as
appropriate for the host CPU architecture. The buildtools update also
brings distinct clang-format executables for mac-x86_64 and mac-arm64 as
appropriate.

Change-Id: I4162b093cfe8d5a2ba66ba62f6462813ea489dbd
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/3700190
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>

DEPS

@@ -14,6 +14,7 @@
 
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
+  'gn_version': 'git_revision:2ecd43a10266bd091c98e6dcde507c64f6a0dad3',
   'pull_linux_clang': False,
   'pull_win_toolchain': False,
   # Controls whether crashpad/build/ios/setup-ios-gn.py is run as part of
@@ -25,7 +26,7 @@ vars = {
 deps = {
   'buildtools':
       Var('chromium_git') + '/chromium/src/buildtools.git@' +
-      '9e121212d42be62a7cce38072f925f8398d11e49',
+      '8b16338d17cd71b04a6ba28da7322ab6739892c2',
   'crashpad/third_party/edo/edo': {
       'url': Var('chromium_git') + '/external/github.com/google/eDistantObject.git@' +
       '727e556705278598fce683522beedbb9946bfda0',
@@ -47,7 +48,37 @@ deps = {
       Var('chromium_git') + '/chromium/src/third_party/zlib@' +
       '13dc246a58e4b72104d35f9b1809af95221ebda7',
 
-  # CIPD packages below.
+  # CIPD packages.
+  'buildtools/linux64': {
+    'packages': [
+      {
+        'package': 'gn/gn/linux-amd64',
+        'version': Var('gn_version'),
+      }
+    ],
+    'dep_type': 'cipd',
+    'condition': 'host_os == "linux"',
+  },
+  'buildtools/mac': {
+    'packages': [
+      {
+        'package': 'gn/gn/mac-${{arch}}',
+        'version': Var('gn_version'),
+      }
+    ],
+    'dep_type': 'cipd',
+    'condition': 'host_os == "mac"',
+  },
+  'buildtools/win': {
+    'packages': [
+      {
+        'package': 'gn/gn/windows-amd64',
+        'version': Var('gn_version'),
+      }
+    ],
+    'dep_type': 'cipd',
+    'condition': 'host_os == "win"',
+  },
   'crashpad/third_party/linux/clang/linux-amd64': {
     'packages': [
       {
@@ -125,7 +156,9 @@ hooks = [
       '--no_auth',
       '--bucket=chromium-clang-format',
       '--sha1_file',
-      'buildtools/mac/clang-format.sha1',
+      'buildtools/mac/clang-format.{host_cpu}.sha1',
+      '--output',
+      'buildtools/mac/clang-format',
     ],
   },
   {