Add an mb configuration for a Win32 ARM64 builder.

Bug: 925575
Change-Id: Ia337a7a22f1b60523257e6eb037536b7ef55bf15
Reviewed-on: https://chromium-review.googlesource.com/c/1457220
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Auto-Submit: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629805}

tools/mb/mb_config.pyl

@@ -292,6 +292,7 @@
       'Windows Clang deterministic': 'clang_release_bot_minimal_symbols_x86',
       'win-annotator-rel': 'release_bot',
       'win-autofill-captured-sites-rel': 'release_bot',
+      'win32-arm64-rel': 'win32_arm64_release_bot',
     },
 
     'chromium.goma': {
@@ -1829,6 +1830,10 @@
       'no_clang', 'release_bot',
     ],
 
+    'win32_arm64_release_bot': [
+      'arm64', 'disable_nacl', 'release_bot',
+    ],
+
     'clang_tot_win_release_cross': [
       'clang_tot', 'win_cross', 'minimal_symbols', 'shared', 'release', 'dcheck_always_on',
     ],