[ci][vs] Enable ASAN docker-sonic-vs image build in PR pipeline

The PR pipeline (azure-pipelines.yml, BuildVS stage) invokes
azure-pipelines-build.yml with an inline jobGroups entry for 'vs' that
carried no variables, so asan_image kept the top-level default 'no' and
the ENABLE_ASAN=y branch in the 'Build sonic image' step was skipped.

The nightly VS pipeline (official-build.yml) passes no jobGroups and
therefore falls through to the template's default jobGroups block, where
the vs group sets asan_image: yes -- which is why nightly produces
target/docker-sonic-vs-asan.gz but PR builds did not.

Set asan_image: yes on the vs jobGroup so PR VS builds also produce
docker-sonic-vs-asan.gz (published via the existing 'mv target/*' step).

Signed-off-by: securely1g <securely1g@users.noreply.github.com>

Author: securely1g

azure-pipelines.yml

@@ -67,6 +67,8 @@ stages:
       buildOptions: 'USERNAME=admin SONIC_BUILD_JOBS=$(nproc) BUILD_MULTIASIC_KVM=y INCLUDE_DHCP_SERVER=y ${{ variables.VERSION_CONTROL_OPTIONS }}'
       jobGroups:
       - name: vs
+        variables:
+          asan_image: yes
   - template: .azure-pipelines/azure-pipelines-build.yml
     parameters:
       buildOptions: 'USERNAME=admin SONIC_BUILD_JOBS=$(nproc) ${{ variables.VERSION_CONTROL_OPTIONS }}'