Cleanup test_remove. NFC (emscripten-core#23081)

- Convert to C.
- Move to `test/stdio`

This test was originally added in c008b11 and is not specific to C++
cstdio and was the only file in this directory.

Also remove the cleanup code.  See emscripten-core#23003.

test/cstdio/test_remove.cpp → test/stdio/test_remove.c

@@ -5,8 +5,7 @@
 
 #include <assert.h>
 #include <errno.h>
-#include <cstdio>
-#include <iostream>
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 #include <stdlib.h>
@@ -30,38 +29,29 @@ void setup() {
   mkdir("dir/subdir", 0777);
 }
 
-void cleanup() {
-  // make sure we get it all regardless of anything failing
-  unlink("file");
-  unlink("dir/file");
-  rmdir("dir/subdir");
-  rmdir("dir");
-}
-
 void test() {
   int err;
-  
-  err = std::remove("dir/file");
+
+  err = remove("dir/file");
   assert(!err);
 
-  err = std::remove("file");
+  err = remove("file");
   assert(!err);
 
   // should fail, folder is not empty
-  err = std::remove("dir");
+  err = remove("dir");
   assert(err);
 
-  err = std::remove("dir/subdir");
+  err = remove("dir/subdir");
   assert(!err);
 
-  err = std::remove("dir");
+  err = remove("dir");
   assert(!err);
 
-  std::cout << "success\n";
+  printf("success\n");
 }
 
 int main() {
-  atexit(cleanup);
   setup();
   test();
   return 0;

test/test_core.py

@@ -1697,7 +1697,7 @@ def test_rename(self):
     self.do_run_in_out_file_test('stdio/test_rename.c')
 
   def test_remove(self):
-   self.do_run_in_out_file_test('cstdio/test_remove.cpp')
+   self.do_run_in_out_file_test('stdio/test_remove.c')
 
   def test_alloca_stack(self):
     self.do_core_test('test_alloca_stack.c')