Compress binary tarballs using xz

Fixes #240.

Apparently 'tar -xf' can decompress xz files on macOS nowadays.

release.nix

@@ -165,10 +165,10 @@ let
           chmod +x $TMPDIR/install-systemd-multi-user.sh
           chmod +x $TMPDIR/install-multi-user
           dir=nix-${version}-${system}
-          fn=$out/$dir.tar.bz2
+          fn=$out/$dir.tar.xz
           mkdir -p $out/nix-support
           echo "file binary-dist $fn" >> $out/nix-support/hydra-build-products
-          tar cvfj $fn \
+          tar cvfJ $fn \
             --owner=0 --group=0 --mode=u+rw,uga+r \
             --absolute-names \
             --hard-dereference \
@@ -295,7 +295,7 @@ let
 
           substitute ${./scripts/install.in} $out/install \
             ${pkgs.lib.concatMapStrings
-              (system: "--replace '@binaryTarball_${system}@' $(nix hash-file --base16 --type sha256 ${binaryTarball.${system}}/*.tar.bz2) ")
+              (system: "--replace '@binaryTarball_${system}@' $(nix hash-file --base16 --type sha256 ${binaryTarball.${system}}/*.tar.xz) ")
               [ "x86_64-linux" "i686-linux" "x86_64-darwin" "aarch64-linux" ]
             } \
             --replace '@nixVersion@' ${build.x86_64-linux.src.version}

scripts/install.in

@@ -30,12 +30,11 @@ case "$(uname -s).$(uname -m)" in
     *) oops "sorry, there is no binary distribution of Nix for your platform";;
 esac
 
-url="https://nixos.org/releases/nix/nix-@nixVersion@/nix-@nixVersion@-$system.tar.bz2"
+url="https://nixos.org/releases/nix/nix-@nixVersion@/nix-@nixVersion@-$system.tar.xz"
 
-tarball="$tmpDir/$(basename "$tmpDir/nix-@nixVersion@-$system.tar.bz2")"
+tarball="$tmpDir/$(basename "$tmpDir/nix-@nixVersion@-$system.tar.xz")"
 
 require_util curl "download the binary tarball"
-require_util bzcat "decompress the binary tarball"
 require_util tar "unpack the binary tarball"
 
 echo "downloading Nix @nixVersion@ binary tarball for $system from '$url' to '$tmpDir'..."
@@ -57,7 +56,7 @@ fi
 
 unpack=$tmpDir/unpack
 mkdir -p "$unpack"
-< "$tarball" bzcat | tar -xf - -C "$unpack" || oops "failed to unpack '$url'"
+tar -xf "$tarball" -C "$unpack" || oops "failed to unpack '$url'"
 
 script=$(echo "$unpack"/*/install)