gitlab-ci: Use separate docker images for x86 build/test jobs

Same as was done for the ARM images before.

This should make it less painful to update to newer dEQP / piglit as
well as to make changes to the build/test environment.

Reviewed-by: Eric Anholt <eric@anholt.net>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f4715b9..f3421a8 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -14,13 +14,15 @@
 # repository's registry will be used there as well.
 variables:
   UPSTREAM_REPO: mesa/mesa
-  DEBIAN_TAG: "2019-11-12"
+  DEBIAN_TAG: "amd64-2019-11-12"
+  DEBIAN_TEST_TAG: "amd64-test-2019-11-12"
   DEBIAN_ARM64_TAG: "arm64v8-2019-11-06"
   DEBIAN_ARM64_TEST_TAG: "arm64v8-test-2019-11-12"
   STRETCH_TAG: "2019-09-18"
   DEBIAN_VERSION: buster-slim
   STRETCH_VERSION: stretch-slim
   DEBIAN_IMAGE: "$CI_REGISTRY_IMAGE/debian/$DEBIAN_VERSION:$DEBIAN_TAG"
+  DEBIAN_TEST_IMAGE: "$CI_REGISTRY_IMAGE/debian/$DEBIAN_VERSION:$DEBIAN_TEST_TAG"
   DEBIAN_ARM64_IMAGE: "$CI_REGISTRY_IMAGE/debian/$DEBIAN_VERSION:$DEBIAN_ARM64_TAG"
   DEBIAN_ARM64_TEST_IMAGE: "$CI_REGISTRY_IMAGE/debian/$DEBIAN_VERSION:$DEBIAN_ARM64_TEST_TAG"
   STRETCH_IMAGE: "$CI_REGISTRY_IMAGE/debian/$STRETCH_VERSION:$STRETCH_TAG"
@@ -99,6 +101,12 @@
   needs:
     - debian-10:amd64
 
+debian-10-test:amd64:
+  extends: debian-10:amd64
+  variables:
+    DEBIAN_TAG: "$DEBIAN_TEST_TAG"
+    DEBIAN_EXEC: 'bash .gitlab-ci/debian-test-install.sh'
+
 debian-9:amd64:
   extends: debian-10:amd64
   variables:
@@ -447,7 +455,7 @@
 .test:
   extends:
     - .ci-run-policy
-    - .use-debian-10:amd64
+  image: $DEBIAN_TEST_IMAGE
   stage: test
   variables:
     GIT_STRATEGY: none # testing doesn't build anything from source
@@ -465,7 +473,7 @@
     - meson-main
   needs:
     - meson-main
-    - debian-10:amd64
+    - debian-10-test:amd64
 
 .piglit-test:
   extends: .test