[mjsunit] Prevent module test from accidentally loading common files

- Disable automatic module file extensions for the test
- Use uncommon name suffix to prevent accidental loading of an
  existing file

Change-Id: I26c1092a1e559cbbebce442a8d5ff3fb6dd5aa84
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3122145Reviewed-by: Patrick Thier <pthier@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76616}

src/d8/d8.cc

@@ -4379,8 +4379,9 @@ bool Shell::SetOptions(int argc, char* argv[]) {
       options.fuzzilli_coverage_statistics = true;
       argv[i] = nullptr;
 #endif
-    } else if (strcmp(argv[i], "--fuzzy-module-file-extensions") == 0) {
-      options.fuzzy_module_file_extensions = true;
+    } else if (strcmp(argv[i], "--no-fuzzy-module-file-extensions") == 0) {
+      DCHECK(options.fuzzy_module_file_extensions);
+      options.fuzzy_module_file_extensions = false;
       argv[i] = nullptr;
 #if defined(V8_ENABLE_SYSTEM_INSTRUMENTATION)
     } else if (strcmp(argv[i], "--enable-system-instrumentation") == 0) {

test/mjsunit/regress/regress-v8-12060.mjs

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --no-fuzzy-module-file-extensions
+
 const paths = [
   ".",
   "..",
@@ -15,7 +17,8 @@ const paths = [
   "./../..",
 ];
 
-const results = await Promise.allSettled(paths.map(path => import(path)));
+const results = await Promise.allSettled(
+    paths.map(path => import(path + "/___._._")));
 for (let result of results) {
   assertEquals(result.status, 'rejected');
 }