fix(justfile): Ensure `install-pacman-dev-packages` recipe works

Fix the wrong use of the `PACMAN_DEV_PACKAGES` environment
variable in the `install-pacman-dev-packages` recipe (it is called
`PACMAN_PACKAGES`).
Execute `pacman` using `run0` to ensure it can be run without `sudo` on
any newer systemd-based system.
Don't update the system but simply install the packages.

Signed-off-by: David Runge <dvzrv@archlinux.org>

justfile

@@ -26,7 +26,7 @@ dev-install: install-pacman-dev-packages install-rust-dev-tools
 # Installs development packages using pacman
 install-pacman-dev-packages:
     # All packages are set in the `.env` file
-    pacman -Syu --needed --noconfirm $PACMAN_DEV_PACKAGES
+    run0 pacman -S --needed --noconfirm $PACMAN_PACKAGES
 
 # Installs all Rust tools required for development
 install-rust-dev-tools: