AzurePipelines: Add support for ArmPkg

Add an entry to build the ArmPkg in the CI.

Fixes: https://bugzilla.tianocore.org/show_bug.cgi?id=3348
Cc: Bret Barkelew <bret.barkelew@microsoft.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

.azurepipelines/templates/pr-gate-build-job.yml

@@ -21,6 +21,9 @@ jobs:
   #Use matrix to speed up the build process
   strategy:
     matrix:
+      TARGET_ARM:
+        Build.Pkgs: 'ArmPkg'
+        Build.Targets: 'DEBUG,RELEASE,NO-TARGET,NOOPT'
       TARGET_MDE_CPU:
         Build.Pkgs: 'MdePkg,UefiCpuPkg'
         Build.Targets: 'DEBUG,RELEASE,NO-TARGET,NOOPT'