fix multithreading issue in NSTask
fix multithreading issue in NSTask

yuhangwang/cocotron,crystax/android-vendor-cocotron,cneira/cocotron,Suninus/cocotron,Suninus/cocotron,ruppmatt/cocotron,JackLian/cocotron,yuhangwang/cocotron,crystax/android-vendor-cocotron,cneira/cocotron,gemu2015/cocotron-sierra,cyclaero/cocotron,yuhangwang/cocotron,cyclaero/cocotron,guestOS/guestOS,gemu2015/cocotron-sierra,gemu2015/cocotron-sierra,yuhangwang/cocotron,Suninus/cocotron,guestOS/guestOS,crystax/android-vendor-cocotron,JackLian/cocotron,ruppmatt/cocotron,crystax/android-vendor-cocotron,ruppmatt/cocotron,cjwl/cocotron,cjwl/cocotron,guestOS/guestOS,Suninus/cocotron,cyclaero/cocotron,cjwl/cocotron,JackLian/cocotron,cneira/cocotron,cneira/cocotron,cyclaero/cocotron,ruppmatt/cocotron,JackLian/cocotron,guestOS/guestOS,gemu2015/cocotron-sierra,cjwl/cocotron