Makefile does not overwrite par2 path
if par2 is available on build-host it is detected
and then the patch with fixup-config-pl.patch
in install fails because hunk 2 cannot be applied

hunk 2 has $Conf{ParPath}   = ''; - so provide an empty path

Signed-off-by: Dirk Neukirchen <plntyk.lede@plntyk.name>