Update rescript_format.js

Author: cristianoc

scripts/rescript_format.js

@@ -126,7 +126,7 @@ function main(argv, rescript_exe, bsc_exe) {
         );
         (async function () {
           var content = await readStdin();
-          var fd = fs.openSync(filename, "wx", 0o600);
+          var fd = fs.openSync(filename, "wx", 0o600); // Avoid overwriting existing file
           fs.writeFileSync(fd, content, "utf8");
           fs.closeSync(fd);
           process.addListener("exit", () => fs.unlinkSync(filename));