MB: Add configs for Windows bots enforcing MSVC compilation.

tools_webrtc/mb/mb_config.pyl

Index: tools_webrtc/mb/mb_config.pyl
diff --git a/tools_webrtc/mb/mb_config.pyl b/tools_webrtc/mb/mb_config.pyl
index 03d05f6d0052737878674ffb077ab279c1714c05..37f87e83abcb85e408e95c2a359dfefdbabfb749 100644
--- a/tools_webrtc/mb/mb_config.pyl
+++ b/tools_webrtc/mb/mb_config.pyl
@@ -74,6 +74,7 @@
       'Win64 Debug (Clang)': 'win_clang_debug_bot_x64',
       'Win64 Release (Clang)': 'win_clang_release_bot_x64',
       'Win32 ASan': 'win_asan_clang_release_bot_x86',
+      'Win32 Release (MSVC)': 'win_msvc_release_bot_x86',
       'Win32 Release [large tests]': 'release_bot_x86',
     },
     'client.webrtc.perf': {
@@ -187,6 +188,7 @@
       'win_x64_clang_dbg': 'win_clang_debug_bot_x64',
       'win_x64_clang_rel': 'win_clang_release_bot_x64',
       'win_asan': 'win_asan_clang_release_bot_x86',
+      'win_msvc_rel': 'win_msvc_release_bot_x86',
       'win_baremetal': 'release_bot_x86',
       'win_x64_win8': 'debug_bot_x64',
       'win_x64_win10': 'debug_bot_x64',
@@ -279,6 +281,9 @@
     'win_clang_release_bot_x64': [
       'gn', 'clang', 'openh264_release_bot', 'x64',
     ],
+    'win_msvc_release_bot_x86': [
+      'gn', 'no_clang', 'openh264_release_bot', 'x86',
+    ],
     'win_asan_clang_release_bot_x86': [
       'gn', 'asan', 'clang',  'full_symbols', 'openh264_release_bot', 'x86',
       'win_fastlink',
@@ -421,6 +426,10 @@
                   'use_prebuilt_instrumented_libraries=true'),
     },
 
+    'no_clang': {
+      'gn_args': 'is_clang=false',
+    },
+
     'no_rtc_tests': {
       'gn_args': 'rtc_include_tests=false',
     },