[D-runtime] [dlang/druntime] 2ebc2f: fix building non-PR builds

[GitHub via D-runtime]

  Branch: refs/heads/master
  Home:   https://github.com/dlang/druntime
  Commit: 2ebc2fba6c03f42a158a70e3df5bb075e570e713
      https://github.com/dlang/druntime/commit/2ebc2fba6c03f42a158a70e3df5bb075e570e713
  Author: Martin Nowak <code at dawg.eu>
  Date:   2016-09-23 (Fri, 23 Sep 2016)

  Changed paths:
    M circleci.sh

  Log Message:
  -----------
  fix building non-PR builds

- i.e. fix checking for empty/unbound CIRCLECI_PR_NUMBER


  Commit: 0d0ee2c2b00e113d4d258b8ff31a9e730f990b90
      https://github.com/dlang/druntime/commit/0d0ee2c2b00e113d4d258b8ff31a9e730f990b90
  Author: Martin Nowak <code at dawg.eu>
  Date:   2016-09-23 (Fri, 23 Sep 2016)

  Changed paths:
    M circleci.sh

  Log Message:
  -----------
  Merge pull request #1658 from MartinNowak/fix_circleci_branch_builds

fix building non-PR builds


Compare: https://github.com/dlang/druntime/compare/5c9b0e89d509...0d0ee2c2b00e