[CI] Use the same template in PR-build pipeline and official-build pipeline

Signed-off-by: liushilongbuaa <shilongliu@microsoft.com>

azure-pipelines.yml

@@ -18,6 +18,25 @@ resources:
 stages:
 - stage: Build
   pool: sonicbld
+  variables:
+    CACHE_MODE: rcache
+    ${{ if eq(variables['Build.SourceBranchName'], '202012') }}:
+      VERSION_CONTROL_OPTIONS: 'SONIC_VERSION_CONTROL_COMPONENTS=deb,py2,py3,web'
+  jobs:
+  - template: .azure-pipelines/azure-pipelines-build.yml
+    parameters:
+      buildOptions: 'USERNAME=admin SONIC_BUILD_JOBS=$(nproc) ${{ variables.VERSION_CONTROL_OPTIONS }}'
+      jobFilters:
+      - vs
+      - broadcom
+      - mellanox
+
+- stage: Test
+  variables:
+  - name: inventory
+    value: veos_vtb
+  - name: testbed_file
+    value: vtestbed.csv
 
   jobs:
   - job: