CI: don't build the binary toolchains in bootstrap

This job just exercises the binary toolchain packages, so there's no
need to do it in the bootstrap stage.

Change-Id: I9d1697791a1e427d594bd8d99c5cad45961f4c5b
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

.gitlab-ci.yml

@@ -68,10 +68,6 @@ machine-coverage:
   - ./ci/check-machine-coverage
   coverage: '/Coverage: \d+/'
 
-toolchains:
-  extends: .build
-  stage: bootstrap
-
 #
 # Build stage, the actual build jobs
 #
@@ -191,6 +187,9 @@ tc0:
 tc1:
   extends: .build
 
+toolchains:
+  extends: .build
+
 
 #
 # Utility tasks, not executed automatically