freicoin: fix build

Changed files
+2
pkgs
applications
altcoins
+2
pkgs/applications/altcoins/freicoin.nix
···
# I think that openssl and zlib are required, but come through other
# packages
+
preBuild = "unset AR";
+
installPhase = ''
mkdir -p $out/bin
cp freicoin-qt $out/bin