tests/tests.c: open text file in binary mode

If the file is opened and read in text mode in Windows, the line endings
will be translated and thus the stat() and fread() return different
sizes.

Author: yegorich

tests/tests.c

@@ -121,7 +121,7 @@ static const char *read_file_to_string(const char *file)
   buf = (char *)malloc(size + 1);
   TT_ASSERT_PTR_NOTNULL(buf);
 
-  fp = fopen(file, "rt");
+  fp = fopen(file, "rb");
   TT_ASSERT_PTR_NOTNULL(fp);
 
   r = fread(buf, 1, size, fp);