tf-a-builder.yaml: smart clone qa-tools repository

While reverting [1] would be the fastest way to re-enable the qa-tools
repository [2], this is too expensive in terms of CI latency: repository
is cloned per tf-a-builder job but ultimately it is only needed when
running code coverage test descriptions, i.e. tf-l3-code-coverage/*.

This commit clones the repository only when code coverage reports are
required.

[1]
https://git.trustedfirmware.org/ci/tf-a-job-configs.git/commit/?id=2c7f7aedc03ebb24ed072685e371a027de22be53
[2] https://git.gitlab.arm.com/tooling/qa-tools.git

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I9687253762f5b7765538712c2ea629c442ff4423
diff --git a/tf-a-builder.yaml b/tf-a-builder.yaml
index 17ac742..e334896 100644
--- a/tf-a-builder.yaml
+++ b/tf-a-builder.yaml
@@ -52,20 +52,6 @@
             skip-tag: true
             shallow-clone: false
             wipe-workspace: false
-- scm:
-    name: qa-tools
-    scm:
-        - git:
-            url: https://git.gitlab.arm.com/tooling/qa-tools.git
-            refspec: master
-            name: origin
-            branches:
-                - master
-            basedir: qa-tools
-            choosing-strategy: gerrit
-            skip-tag: true
-            shallow-clone: true
-            wipe-workspace: false
 - job:
     name: tf-a-builder
     node: docker-amd64-tf-a-bionic
@@ -136,6 +122,9 @@
         - string:
             name: QA_SERVER
             default: 'https://qa-reports.linaro.org'
+        - string:
+            name: QA_TOOLS_REPO
+            default: 'https://git.gitlab.arm.com/tooling/qa-tools.git'
     scm:
         - tf-a-ci-scripts
         - tf-a-job-configs