llvmpipe/ci: set rusticl variables in deqp-runner instead of passing them down from the job

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29851>

.gitlab-ci/common/generate-env.sh

@@ -112,8 +112,6 @@ VARS=(
     RADEON_DEBUG
     RADV_DEBUG
     RADV_PERFTEST
-    RUSTICL_ENABLE
-    RUSTICL_DEBUG
     SKQP_ASSETS_DIR
     SKQP_BACKENDS
     TU_DEBUG

src/gallium/drivers/llvmpipe/ci/deqp-llvmpipe-rusticl.toml

@@ -2,3 +2,5 @@
 piglit_folder = "/piglit"
 profile = "cl"
 process_isolation = true
+  [piglit.env]
+  RUSTICL_ENABLE = "llvmpipe"

src/gallium/drivers/llvmpipe/ci/gitlab-ci.yml

@@ -9,7 +9,6 @@ llvmpipe-piglit-rusticl:
     - debian-testing
     - debian/x86_64_test-gl
   variables:
-    RUSTICL_ENABLE: "llvmpipe"
     DEQP_SUITE: llvmpipe-rusticl
     DEQP_RUNNER_OPTIONS: "--timeout 120.0"
     GPU_VERSION: llvmpipe-rusticl