artiq-zynq: fix SZL path

artiq-zynq.nix

@@ -2,11 +2,6 @@ let
   pkgs = import <nixpkgs> { overlays = [ (import ./artiq-fast/mozilla-overlay.nix) ]; };
   artiq-zynq = import <artiq-zynq>;
   artiq-fast = import <artiq-fast> { inherit pkgs; };
-
-  zynq-rs = import artiq-zynq.zynq-rs;
-  # New zynq-rs versions with Kasli-SoC support have the multiboard "szl" package.
-  # Older versions need the SZL environment variable set to the SZL ELF to be loaded.
-  szlEnv = if zynq-rs ? "szl" then "${zynq-rs.szl}" else "${zynq-rs.zc706-szl}/szl.elf";
 in
   (
     builtins.mapAttrs (key: value: pkgs.lib.hydraJob value) artiq-zynq
@@ -60,7 +55,7 @@ in
 
           export USER=hydra
           export OPENOCD_ZYNQ=${artiq-zynq.zynq-rs}/openocd
-          export SZL=${szlEnv}
+          export SZL=${artiq-zynq.zynq-rs.zc706-szl}/szl.elf
           pushd ${<artiq-zynq>}
           bash ${<artiq-zynq>}/remote_run.sh -h rpi-4 -o "$NIX_SSHOPTS" -d ${artiq-zynq.zc706-nist_qc2-jtag}
           popd