Allow makefile directory to be overridden

Change-Id: I38611e6e8c589329fd0cddafc56234df1840236d

.zuul.yaml

@@ -20,6 +20,7 @@
         http: ""
         https: ""
         noproxy: ""
+      makefile_chdir: "{{ zuul.project.src_dir }}"
       image_config_dir: config
     check:
       jobs:

playbooks/airship-images-build.yaml

@@ -35,7 +35,7 @@
     - name: Publish images
       block:
         - make:
-            chdir: "{{ zuul.project.src_dir }}"
+            chdir: "{{ makefile_chdir }}"
             target: "images"
             params:
               COMMIT: "{{ zuul.newrev | default('') }}"

playbooks/airship-images-publish.yaml

@@ -39,7 +39,7 @@
             password: "{{ airship_images_quay_creds.password }}"
             registry_url: "{{ docker_registry }}"
         - make:
-            chdir: "{{ zuul.project.src_dir }}"
+            chdir: "{{ makefile_chdir }}"
             target: "images"
             params:
               COMMIT: "{{ zuul.newrev | default('') }}"

playbooks/airship-images-test.yaml

@@ -18,7 +18,7 @@
       block:
         - name: "make tests"
           make:
-            chdir: "{{ zuul.project.src_dir }}"
+            chdir: "{{ makefile_chdir }}"
             target: tests
     - name: install libvirt
       include_role: