gioerror: Add conversion from ENXIO to G_IO_ERROR_NOT_REGULAR_FILE

`ENXIO` can be returned from `open(2)` for special files (FIFOs, device
files and domain sockets) which are not backed by anything.

This fixes the error returned by `g_file_replace()` when trying to
replace such a file, so that it now matches the documentation.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

gio/gioerror.c

@@ -107,6 +107,12 @@ g_io_error_from_errno (gint err_no)
       break;
 #endif
 
+#ifdef ENXIO
+    case ENXIO:
+      return G_IO_ERROR_NOT_REGULAR_FILE;
+      break;
+#endif
+
 #ifdef EROFS
     case EROFS:
       return G_IO_ERROR_READ_ONLY;