Add specific mac arm64 mb config

Trying to solve https://ci.chromium.org/ui/p/webrtc/builders/perf/Perf%20Mac%20M1%20Arm64%2012/1/overview

Bug: b/230719743
Change-Id: I43e0206548fe6223552909a23748e3eea678e2a9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/261902
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Christoffer Jansson <jansson@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36837}

tools_webrtc/mb/mb_config.pyl

@@ -127,7 +127,7 @@
       'Perf Linux Bionic': 'release_bot_x64',
       'Perf Linux Trusty': 'release_bot_x64',
       'Perf Mac 11': 'release_bot_x64',
-      'Perf Mac M1 Arm64 12': 'release_bot_arm64',
+      'Perf Mac M1 Arm64 12': 'linux_mac_crosscompile_arm64',
       'Perf Win7': 'release_bot_x64',
     },
     'internal.client.webrtc': {
@@ -276,6 +276,11 @@
       'libfuzzer', 'asan', 'optimize_for_fuzzing', 'openh264',
       'pure_release_bot', 'x64'
     ],
+    'linux_mac_crosscompile_arm64': [
+      'release_bot',
+      'arm64',
+      'mac',
+    ],
     'mac_asan_clang_release_bot_x64': [
       'asan',
       'clang',
@@ -403,6 +408,9 @@
     'lsan': {
       'gn_args': 'is_lsan=true',
     },
+    'mac': {
+      'gn_args': 'target_os="mac"'
+    },
     'minimal_symbols': {
       'gn_args': 'symbol_level=1',
     },