message: Receive additional parameter, set stanc3_bin_url before running tests inside setupCXX
diff: @@ -6,7 +6,10 @@ def skipRemainingStages = false
  def setupCXX(CXX = env.CXX) {
  unstash 'CmdStanSetup'
  - writeFile(file: "make/local", text: "CXX = ${CXX}\n")
  +
  + stanc3_bin_url = params.stanc3_bin_url ?: "nightly"
  + stanc3_bin_url_str = stanc3_bin_url != "nightly" ? "\nSTANC3_TEST_BIN_URL=${stanc3_bin_url}\n" : ""
  + writeFile(file: "make/local", text: "CXX=${CXX} ${stanc3_bin_url_str}")
  }
  def runTests(String prefix = "") {
  @@ -50,6 +53,8 @@ pipeline {
  description: "Stan PR to test against. Will check out this PR in the downstream Stan repo.")
  string(defaultValue: '', name: 'math_pr',
  description: "Math PR to test against. Will check out this PR in the downstream Math repo.")
  + string(defaultValue: 'nightly', name: 'stanc3_bin_url',
  + description: 'Custom stanc3 binary url')
  }
  environment {
  MAC_CXX = 'clang++'
  