Add test to test_files.c

Author: hoodmane

test/other/test_seek_dev_null.c

@@ -162,6 +162,8 @@ void test_tempfiles() {
   char data[5] = { 10, 30, 20, 11, 88 };
   FILE *n = fopen("/dev/null", "w");
   printf("5 bytes to dev/null: %zu\n", fwrite(data, 1, 5, n));
+  int res = fseek(n, 10, SEEK_CUR);
+  printf("seek /dev/null: %d\n", res);
   fclose(n);
 
   // Test file creation with O_TRUNC (regression test for #16784)

test/other/test_seek_dev_null.out

@@ -12,4 +12,5 @@ seeked=ata.
 seeked=ta.
 fscanfed: 10 - hello
 5 bytes to dev/null: 5
+seek /dev/null: 0
 ok.

test/test_files.c

@@ -15295,6 +15295,3 @@ def test_fp16(self, opts):
 
   def test_embool(self):
     self.do_other_test('test_embool.c')
-
-  def test_seek_dev_null(self):
-    self.do_other_test('test_seek_dev_null.c')