src/vs/platform/environment/common/environmentService.ts/AbstractNativeEnvironmentService/builtinExtensionsPath
class AbstractNativeEnvironmentService:	get builtinExtensionsPath(): string {
		const cliBuiltinExtensionsDir = this.args['builtin-extensions-dir'];
		if (cliBuiltinExtensionsDir) {
			return resolve(cliBuiltinExtensionsDir);
		}

		return normalize(join(FileAccess.asFileUri('').fsPath, '..', 'extensions'));
	}