Broken by ec4a159100 (PR #139638); I forgot darwin again.
ec4a159100
@ -19,7 +19,9 @@ let
makeFlags = [ "PREFIX=$(out)" "INSTALLPREFIX=$(out)" ];
postInstall = ''chmod +x "$out"/lib/libminiupnpc.so'';
postInstall = ''
chmod +x "$out"/lib/libminiupnpc${stdenv.hostPlatform.extensions.sharedLibrary}
'';
meta = with lib; {
homepage = "http://miniupnp.free.fr/";