Enable git automatic thread count detection

The repo build process does many git clone operations. This patch
ensures that the repo server git configuration allows git to detect
and make use of the number of CPU which are present, which
benefits operations such as check out which are highly threaded.

Change-Id: Ib01fc1c560dcb9261c328841d7472c87434edab0

tasks/repo_post_install.yml

@@ -13,6 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Enable git automatic thread count detection
+  git_config:
+    scope: system
+    name: pack.threads
+    value: 0
+
 - name: Remove old key file(s) if found
   file:
     path: "{{ item }}"