support parallel build.
support parallel build.

yoku0825/mroonga,mroonga/mroonga,mroonga/mroonga,mroonga/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga,naoa/mroonga,naoa/mroonga,yoku0825/mroonga,yoku0825/mroonga,mroonga/mroonga,yoku0825/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga