AzurePipelines: Add support for ArmPlatformPkg
    
    Add an entry to build the ArmPlatformPkg in the CI.
    
    Fixes: https://bugzilla.tianocore.org/show_bug.cgi?id=3349
    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>