Merged PR 11164011: Make branch to get LKG compiler from configurable

## Description:

+ To target vpack generation to downlevel branches with differing LKG versions, make the target branch configurable in the ADO UI.

Author: samuel-lee-msft

.pipelines/OneBranch.WindowsUndocked.Official.yml

@@ -39,14 +39,18 @@ parameters:
   type: boolean
   displayName: Create VPack
   default: false
+- name: lkgCompilerBranch
+  type: string
+  displayName: Branch from which to get LKG compiler
+  default: 'official/main'
 # - name: ingest
 #   type: boolean
 #   displayName: Create Ingest PR
 #   default: false
 # - name: branch
 #   type: string
 #   displayName: Branch to PR to
-#   default: official/rs_ens1_cs1
+#   default: 'official/rs_ens1_cs1'
 # - name: title
 #   type: string
 #   displayName: PR Title
@@ -87,6 +91,7 @@ extends:
           description: 'SymCrypt cryptographic library'
           owner: '[email protected]'
           sign: true
+          lkgCompilerBranch: ${{ parameters.lkgCompilerBranch }}
           # Windows ingestion args
           # ingest: ${{ parameters.ingest }}
           # osPath: 'onecore/ds/security/symcrypt'