Manually download the lix installer

This uses curl's --etag-save and --etag-compare functions to see if we need a new installer and only then download it.

do-the-lix-thing

@@ -16,6 +16,7 @@ set -o pipefail # the return value of a pipeline is the status of
 # Constants
 REPO_URL="https://github.com/samueldr/lix-gha-installer-action"
 ACTION_NAME="Lix GHA Installer Action"
+INSTALLER_DOWNLOAD_DIR="/tmp/lix-installer"
 ################################################################################
 
 
@@ -126,7 +127,15 @@ trap _handle_exit EXIT
 (
 set -x
 
-curl -sSf -L https://install.lix.systems/lix | bash -s -- install --no-confirm
+_installer_bin="$INSTALLER_DOWNLOAD_DIR/lix-installer"
+_etag="$INSTALLER_DOWNLOAD_DIR/etag"
+mkdir -p "$(dirname "$_installer_bin")"
+if ! curl --head -sSf -L --etag-compare "$_etag" "https://install.lix.systems/lix/lix-installer-$(_get_system)"
+then
+	curl -o "$_installer_bin" -sSf -L --etag-save "$_etag" "https://install.lix.systems/lix/lix-installer-$(_get_system)"
+	chmod +x "$_installer_bin"
+fi
+env TERM=dumb "$_installer_bin" install </dev/null
 
 (
 	< /etc/nix/nix.conf sed -e 's/nixpkgs=flake:nixpkgs/nixpkgs=channel:nixos-unstable/'