silence a -Wint-in-bool-context warning:

In file included from /home/runner/work/physfs/physfs/src/physfs.c:12:
/home/runner/work/physfs/physfs/src/physfs.c: In function ‘openDirectory’:
/home/runner/work/physfs/physfs/src/physfs.c:929:40: warning: ?: using integer constants in boolean context [-Wint-in-bool-context]
  929 |     BAIL_IF(!retval, claimed ? errcode : PHYSFS_ERR_UNSUPPORTED, NULL);
      |                      ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/physfs/physfs/src/physfs_internal.h:273:44: note: in definition of macro ‘BAIL_IF’
  273 | #define BAIL_IF(c, e, r) do { if (c) { if (e) PHYSFS_setErrorCode(e); return r; } } while (0)
      |                                            ^

Closes https://github.com/icculus/physfs/issues/44

src/physfs.c

@@ -921,12 +921,12 @@ static DirHandle *openDirectory(PHYSFS_Io *io, const char *d, int forWriting)
             retval = tryOpenDir(io, *i, d, forWriting, &claimed);
     } /* else */
 
-    errcode = currentErrorCode();
+    errcode = claimed ? currentErrorCode() : PHYSFS_ERR_UNSUPPORTED;
 
     if ((!retval) && (created_io))
         io->destroy(io);
 
-    BAIL_IF(!retval, claimed ? errcode : PHYSFS_ERR_UNSUPPORTED, NULL);
+    BAIL_IF(!retval, errcode, NULL);
     return retval;
 } /* openDirectory */