build: set "clang" in config.gypi in GN build

PR-URL: #53004
Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>

tools/generate_config_gypi.py

@@ -79,6 +79,7 @@ def translate_config(out_dir, config, v8_config):
     },
     'variables': {
       'asan': bool_string_to_number(config['is_asan']),
+      'clang': bool_to_number(config['is_clang']),
       'enable_lto': config['use_thin_lto'],
       'is_debug': bool_string_to_number(config['is_debug']),
       'llvm_version': 13,