esp/ci: Update build scripts repo ref to release tag 'esp-20.1.1_20250829'

Author: gerekon

.gitlab-ci.yml

@@ -14,7 +14,7 @@ default:
   interruptible: true
 
 variables:
-  ESP_LLVM_EMBEDDED_TOOLCHAIN_REF: "llvm_release_19"
+  ESP_LLVM_EMBEDDED_TOOLCHAIN_REF: "esp-20.1.1_20250829"
   ESP_GNU_TOOLCHAIN_VER: "14.2.0_20241119"
   CROSS_ARM_IMAGE: $CI_DOCKER_REGISTRY/llvm-build-cross-arm:2
   CROSS_WIN_IMAGE: $CI_DOCKER_REGISTRY/llvm-build-cross-win:3