message: [lldb-dotest] Set both swift compiler and library
  This change will allow us to remove the SWIFTCC and SWIFTLIBS
  environment variables from the swift build script.
diff: #!/usr/bin/env python
  +import os
  import subprocess
  import sys
  dotest_path = '@LLDB_SOURCE_DIR@/test/dotest.py'
  dotest_args_str = '@LLDB_DOTEST_ARGS@'
  -swiftc = '@LLDB_SWIFTC@'
  +
  +swift_build_dir = '@LLDB_PATH_TO_SWIFT_BUILD'
  +swift_compiler = os.path.join(swift_build_dir, 'bin', 'swiftc')
  +swift_library = os.path.join(swift_build_dir, 'lib', 'swift')
  if __name__ == '__main__':
  wrapper_args = sys.argv[1:]
  @@ -12,7 +16,8 @@ if __name__ == '__main__':
  # Build dotest.py command.
  cmd = [dotest_path, '-q']
  cmd.extend(dotest_args)
  - cmd.extend(['--swift-compiler', swifc])
  + cmd.extend(['--swift-compiler', swift_compiler])
  + cmd.extend(['--swift-library', swift_library])
  cmd.extend(wrapper_args)
  # Invoke dotest.py
  subprocess.call(cmd)
  