[gjs/ewlsh/allocate-nullptrs] Fix IWYU CI job.

[Evan Welsh <ewlsh src gnome org>]

commit a5d7f686453ceb34188bcc6b233576e29fc3a7a1
Author: Evan Welsh <contact evanwelsh com>
Date:   Fri Sep 3 23:59:34 2021 -0700

    Fix IWYU CI job.
    
    It appears disabling pch was not being passed correctly.

 .gitlab-ci.yml | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 14cf2f1c..cc531dad 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -253,11 +253,9 @@ iwyu:
   when: on_success
   stage: source_check
   image: registry.gitlab.gnome.org/gnome/gjs:fedora.mozjs78-debug
-  variables:
-    CONFIG_OPTS: -Db_pch=false
   script:
     - test/test-ci.sh UPSTREAM_BASE
-    - meson setup _build
+    - meson setup _build -Db_pch=false
     - include-what-you-use --version
     - ./tools/run_iwyu.sh ci-upstream-base
   only: