Build third_party parallelized with all possible cores when ninja is not found (#717)
Build third_party parallelized with all possible cores when ninja is not found (#717)

* Build third_party parallelized with all possible cores when ninja is not found

* add support for mac os x

rsas/souper,jubitaneja/souper,rsas/souper,jubitaneja/souper,jubitaneja/souper,rsas/souper,regehr/souper,rsas/souper,google/souper,regehr/souper,google/souper,jubitaneja/souper,regehr/souper,google/souper,google/souper,regehr/souper,regehr/souper,jubitaneja/souper,rsas/souper,google/souper,jubitaneja/souper,rsas/souper