Merge pull request 'install.sh: improvements' (#1500) from DavHau-install-dev into main

pkgs/gui-installer/gui-installer.sh

@@ -8,8 +8,9 @@ clean_temp_dir() {
   rm -rf "$temp_dir"
 }
 
-is_nix_installed() {
-  if [ -n "$(command -v nix)" ]; then
+is_installed() {
+  name=$1
+  if [ -n "$(command -v "$name")" ]; then
     return 0
   else
     return 1
@@ -17,9 +18,18 @@ is_nix_installed() {
 }
 
 install_nix() {
+  if is_installed curl; then
     curl --proto '=https' --tlsv1.2 -sSf -L \
         https://install.determinate.systems/nix \
       > "$temp_dir"/install_nix.sh
+  elif is_installed wget; then
+    wget -qO- \
+        https://install.determinate.systems/nix \
+      > "$temp_dir"/install_nix.sh
+  else
+    echo "Either curl or wget is required to install Nix. Exiting."
+    exit 1
+  fi
   NIX_INSTALLER_DIAGNOSTIC_ENDPOINT="" sh "$temp_dir"/install_nix.sh install
 }
 
@@ -35,12 +45,13 @@ ask_then_install_nix() {
 }
 
 ensure_nix_installed() {
-  if ! is_nix_installed; then
+  if ! is_installed nix; then
     ask_then_install_nix
   fi
 }
 
 start_clan_gui() {
+  PATH="${PATH:+$PATH:}/nix/var/nix/profiles/default/bin" \
     exec nix run \
       https://git.clan.lol/clan/clan-core/archive/main.tar.gz#clan-vm-manager \
       --no-accept-flake-config \