make: jobserver unavailable: using -j1

   这个是在使用并行编译的时候发生的，http://www.delorie.com/gnu/docs/make/make_130.html

 

warning: jobserver unavailable: using -j1. Add `+' to parent make rule.'

In order for  make processes to communicate, the parent will pass information to the child. Since this could result in problems if the child process isn't actually a  make, the parent will only do this if it thinks the child is a  make. The parent uses the normal algorithms to determine this (see section  How the  MAKE Variable Works). If the makefile is constructed such that the parent doesn't know the child is a  make process, then the child will receive only part of the information necessary. In this case, the child will generate this warning message and proceed with its build in a sequential manner.