[build] Switch win-clang to msvs after default has changed

This ports:
https://chromium-review.googlesource.com/c/chromium/src/+/732997

NOTRY=true

Bug: chromium:781724
Change-Id: Ib57e94bfa66f7898c10b14ce0c07a12b0c3d25b8
Reviewed-on: https://chromium-review.googlesource.com/753725
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49140}

infra/mb/mb_config.pyl

@@ -77,8 +77,8 @@
       'V8 Win32 ASAN': 'gn_release_x86_asan_no_lsan',
       'V8 Win64': 'gn_release_x64_minimal_symbols',
       'V8 Win64 - debug': 'gn_debug_x64_minimal_symbols',
-      # TODO(machenbach): Switch plugins on when errors are fixed.
-      'V8 Win64 - clang': 'gn_release_x64_clang',
+      # TODO(machenbach): Rename bot to msvc.
+      'V8 Win64 - clang': 'gn_release_x64_msvc',
       # Mac.
       'V8 Mac': 'gn_release_x86',
       'V8 Mac - debug': 'gn_debug_x86',
@@ -218,7 +218,8 @@
       'v8_win_rel_ng': 'gn_release_x86_trybot',
       'v8_win_nosnap_shared_rel_ng':
         'gn_release_x86_no_snap_shared_minimal_symbols',
-      'v8_win64_clang_compile_rel': 'gn_release_x64_clang',
+      # TODO(machenbach): Rename bot to msvc.
+      'v8_win64_clang_compile_rel': 'gn_release_x64_msvc',
       'v8_win64_dbg': 'gn_debug_x64_minimal_symbols',
       'v8_win64_rel_ng': 'gn_release_x64_trybot',
       'v8_mac_rel_ng': 'gn_release_x86_trybot',
@@ -407,8 +408,8 @@
       'gn', 'release_bot', 'x64', 'cfi', 'swarming'],
     'gn_release_x64_cfi_clusterfuzz': [
       'gn', 'release_bot', 'x64', 'cfi_clusterfuzz'],
-    'gn_release_x64_clang': [
-      'gn', 'release_bot', 'x64', 'clang', 'swarming'],
+    'gn_release_x64_msvc': [
+      'gn', 'release_bot', 'x64', 'msvc', 'swarming'],
     'gn_release_x64_concurrent_marking': [
       'gn', 'release_bot', 'x64', 'v8_enable_concurrent_marking', 'swarming'],
     'gn_release_x64_correctness_fuzzer' : [
@@ -666,6 +667,10 @@
                   'use_prebuilt_instrumented_libraries=true'),
     },
 
+    'msvc': {
+      'gn_args': 'is_clang=false',
+    },
+
     # TODO(machenbach): Remove when http://crbug.com/738814 is resolved.
     'no_custom_libcxx': {
       'gn_args': 'use_custom_libcxx=false',