'--jobs' flag and dependencies

[Frank Schaefer]

Dear 'make' team, 

I found an issue with your make utility when applying multiple 
jobs (--jobs=10 for example). The problem is that 'make' seems
to start building a target as soon as the dependency has been 
started to be built, e.g.

dep0:
     build dep0

dep1:
     build dep1

target: dep0 dep1 
     build target


... might end up in a sequence like this:
(best viewed with mono-spaced font)


       target               dep0                 dep1
          |                   |                    |
          |               build dep0               |
          |               //////////           build dep1
          |               //////////           //////////
          |               terminated           //////////
     build target             |                //////////
     ... ERROR ..             |                terminated
          |                   |                    |
          |                   |                    |    
 
that is, when the target is built the dep1 is not yet completed
and the dependency cannot be fulfilled. Thus: 

+--------------------------------------------------------------------+
| The build process/thread of a target shall only be started when    |
| the build process of the every dependecy has terminated.           |
+--------------------------------------------------------------------+

This way one does not have to write bottle-neck phony targets by
hand to solve this problem.

Best Regards

Frank Schaefer