[all-commits] [llvm/llvm-project] 2159ed: [libc++][ci] Update how we build the Docker image

[Louis Dionne via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 2159ed811f96cb1aefecf3369d80e69e06fd32a3
      https://github.com/llvm/llvm-project/commit/2159ed811f96cb1aefecf3369d80e69e06fd32a3
  Author: Louis Dionne <ldionne at apple.com>
  Date:   2020-09-29 (Tue, 29 Sep 2020)

  Changed paths:
    M libcxx/utils/ci/Dockerfile

  Log Message:
  -----------
  [libc++][ci] Update how we build the Docker image

This fixes a couple of issues, such as failing filesystem tests (due to
running the tests as root), and not running with the GCC we downloaded.