BaseTools: Add LogAgent to support multiple process Autogen

BaseTools: Add LogAgent to support multiple process Autogen

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1875

AutoGen processes race the logfile. To resolve this issue,
this patch create a LogAgent thread in main process to write
the log content to console or file, Other process will send
the log content to the LogAgent.

Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Liming Gao <liming.gao@intel.com>