fix in template file set system env

Author: frank-dong-ms

build/ci/job-template.yml

@@ -45,7 +45,7 @@ jobs:
     - ${{ if eq(parameters.pool.name, 'Hosted macOS High Sierra') }}:
       - script: brew update && brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/f5b1ac99a7fba27c19cee0bc4f036775c889b359/Formula/libomp.rb && brew install mono-libgdiplus gettext && brew link gettext --force && brew link libomp --force
         displayName: Install build dependencies
-    - bash: echo "##vso[task.setvariable variable=LD_LIBRARY_PATH]$(nightlyBuildRunPath):LD_LIBRARY_PATH"
+    - bash: echo "##vso[task.setvariable variable=LD_LIBRARY_PATH]$(nightlyBuildRunPath):$LD_LIBRARY_PATH"
       displayName: Set LD_LIBRARY_PATH for Ubuntu to locate Native shared library
       condition: ${{ and(eq(parameters.nightlyBuild, 'true'), eq(parameters.name, 'Ubuntu_x64_NetCoreApp21')) }}
     - script: ${{ parameters.buildScript }} -$(_configuration) -buildArch=${{ parameters.architecture }}