mkSymlinkActivationScript: add overall check for existence of source

flake.nix

@@ -12,10 +12,12 @@
     ];
 
     mkSymlinkActivationScript = {target, source}: ''
+      if [ -e ${source} ]; then
         if [ -e ${target} ]; then
           rm -rf ${target}
         fi
         ln -s ${source} ${target}
+      fi
     '';
 
     attrByStrPath = strPath: set: nixpkgs.lib.attrByPath (nixpkgs.lib.strings.splitString "." strPath) null set;