solanum: disable install parallelism

Without the change parallel installs fail as:

...-binutils-2.40/bin/ld: cannot find ./.libs/libircd.so: No such file or directory
collect2: error: ld returned 1 exit status
make[4]: *** [Makefile:634: solanum] Error 1

+5
+5
pkgs/servers/irc/solanum/default.nix
··· 57 57 doCheck = !stdenv.isDarwin; 58 58 59 59 enableParallelBuilding = true; 60 + # Missing install depends: 61 + # ...-binutils-2.40/bin/ld: cannot find ./.libs/libircd.so: No such file or directory 62 + # collect2: error: ld returned 1 exit status 63 + # make[4]: *** [Makefile:634: solanum] Error 1 64 + enableParallelInstalling = false; 60 65 61 66 meta = with lib; { 62 67 description = "An IRCd for unified networks";