Import Perforce jam @8017:
Interix (OpenNT) client port.
Broken in two ways: $TEMP must be reset so as not to be
the dumb DOS path, and their $CWD syntax //D/path conflicts
with ours client syntax, making it impossible to refer to
local files using local, full pathnames. The client root
must be set to /path (without the leading //D), limiting the
client to the current drive.