tools: fix build at non-English windows

PR-URL: #30492
Fixes: #25885
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

Author: pd4d10

tools/v8_gypfiles/v8.gyp

@@ -99,6 +99,13 @@
     ],
   },
   'includes': ['toolchain.gypi', 'features.gypi'],
+  'target_defaults': {
+    'msvs_settings': {
+      'VCCLCompilerTool': {
+        'AdditionalOptions': ['/utf-8']
+      }
+    },
+  },
   'targets': [
     {
       'target_name': 'run_torque',