fix(jobPatched): fix variables not being unset if all contain store paths

the goal was to remove "variables" when it's empty, but this resulted in
the original value being used if all of the variables contained store
paths. This is not supposed to happen and thus fixed with this.

lib/impl/helpers.nix

@@ -2,7 +2,21 @@
   pkgs,
   lib,
 } @ args: let
-  inherit (lib) types isAttrs filterAttrs mapAttrs mkOption mkOptionType isType literalExpression pipe;
+  inherit
+    (lib)
+    types
+    isAttrs
+    filterAttrs
+    mapAttrs
+    mkOption
+    mkOptionType
+    isType
+    literalExpression
+    pipe
+    hasInfix
+    concatMapAttrs
+    optionalAttrs
+    ;
 in rec {
   prepend = key: arr: job: {
     ${key} = arr ++ (job.${key} or []);
@@ -33,10 +47,10 @@ in rec {
 
   # filter job's variables to either only those containing store paths
   # or those that do not
-  filterJobVariables = nix: job:
-    lib.concatMapAttrs (
+  filterJobVariables = shouldContain: job:
+    concatMapAttrs (
       name: value:
-        lib.optionalAttrs ((lib.hasInfix "/nix/store/" value) == nix) {
+        optionalAttrs ((hasInfix "/nix/store/" value) == shouldContain) {
           ${name} = value;
         }
     )

lib/impl/jobPatched.nix

@@ -16,28 +16,16 @@ in
       (prependToBeforeScript ["source setup_nix_ci \"gitlab-ci:pipeline:${pipelineName}:job-deps:${key}\""] job)
       // (appendToAfterScript ["finalize_nix_ci"] job)
     ))
-    // optionalAttrs nixConfig.enable (
-      (let
+    // optionalAttrs nixConfig.enable {
       variables =
         (filterJobVariables false job)
         // optionalAttrs nixConfig.enableRunnerCache {
           NIX_CI_CACHE_STRATEGY = "runner";
         };
-      in
-        # filter empty variables
-        optionalAttrs (variables != {}) {
-          inherit variables;
-        })
-      // (let
       cache =
         (toList (job.cache or []))
         ++ (optional nixConfig.enableRunnerCache {
           key = nixConfig.runnerCacheKey;
           paths = [".nix-cache/"];
         });
-      in
-        # filter empty cache
-        optionalAttrs (cache != []) {
-          inherit cache;
-        })
-    )
+    }