[mutter] ci: Set GIT_STRATEGY: no for some jobs

[Marge Bot <marge-bot src gnome org>]

commit 0a456b4808eb9ccbcedf8020948254d07d4027e4
Author: Michel Dänzer <mdaenzer redhat com>
Date:   Thu Dec 17 15:49:10 2020 +0100

    ci: Set GIT_STRATEGY: no for some jobs
    
    These jobs don't need the Git tree.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1647>

 .gitlab-ci.yml | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 41b2360564..e353627171 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -98,6 +98,8 @@ check-merge-request:
   extends:
     - .fdo.ci-fairy
   stage: review
+  variables:
+    GIT_STRATEGY: none
   script:
     - if [[ x"$CI_MERGE_REQUEST_TARGET_BRANCH_NAME" != "x" ]] ;
       then
@@ -121,6 +123,8 @@ build-fedora-container@x86_64:
   needs:
     - check-commit-log
     - check-merge-request
+  variables:
+    GIT_STRATEGY: none
 
 build-fedora-container@aarch64:
   extends:
@@ -130,6 +134,8 @@ build-fedora-container@aarch64:
   needs:
     - check-commit-log
     - check-merge-request
+  variables:
+    GIT_STRATEGY: none
 
 .build-mutter:
   extends: