try to fix tests

scripts/update-prod-hashbang.mjs

@@ -1,5 +1,6 @@
 #!/usr/bin/env node
 import * as fs from "node:fs";
+import * as fsp from "node:fs/promises";
 import * as path from "node:path";
 
 const __dirname = import.meta.dirname;
@@ -12,4 +13,8 @@ fileContents = `#!/usr/bin/env NODE_NO_WARNINGS=1 node\n${fileContents}`;
 fs.rmSync(filePath);
 fs.writeFileSync(filePath, fileContents, {
   mode: 0o755,
+  flush: true,
 });
+
+// eslint-disable-next-line no-console
+fsp.stat(filePath).then(console.log);

test/general-cli.mjs

@@ -128,8 +128,6 @@ describe("cli operations", function () {
   it("enables nodeJS warnings from the dev entrypoint", async function () {
     let stderr = spawnSync("./src/user-entrypoint.mjs", ["warn"], {
       encoding: "utf8",
-      shell: true,
-      stdio: "pipe",
     }).stderr;
 
     // the dev script should emit warnings
@@ -141,8 +139,6 @@ describe("cli operations", function () {
   it("suppresses nodeJS warnings from the prod entrypoint", async function () {
     let stderr = spawnSync("./dist/cli.cjs", ["warn"], {
       encoding: "utf8",
-      shell: true,
-      stdio: "pipe",
     }).stderr;
 
     // the prod one should not