[CI] Split E2E steps into two

GITHUB env vars are set only from the next step up, not right away.

Author: lukaszstolarczuk

.github/workflows/e2e_nightly.yml

@@ -94,10 +94,14 @@ jobs:
         cp ${{github.workspace}}/ur-repo/build/lib/libur_loader.so* ${{github.workspace}}/sycl_build/lib/
         cp ${{github.workspace}}/ur-repo/build/lib/libur_adapter_cuda.so* ${{github.workspace}}/sycl_build/lib/
 
-    - name: Setup SYCL
+    - name: Set additional env. vars
       run: |
         echo "${{github.workspace}}/sycl_build/bin" >> $GITHUB_PATH
         echo "LD_LIBRARY_PATH=${{github.workspace}}/sycl_build/lib:$LD_LIBRARY_PATH" >> $GITHUB_ENV
+
+    # Running (newly built) sycl-ls sets up some extra variables
+    - name: Setup SYCL variables
+      run: |
         which clang++ sycl-ls
         SYCL_PI_TRACE=-1 sycl-ls