`ninja` with multiple` build.ninja` files?

I would like to run multiple builds ninja

at the same time. Each assembly is in its own directory and has its own file build.ninja

.

I could just do the following:

cd <build-dir-1>
ninja &
cd <build-dir-2>
ninja &
...
cd <build-dir-last>
ninja

      

        
        
        
      

    

.... but there are several problems with this:

• By default, the number of threads used by Ninja is probably not optimal when running multiple independent assemblies at the same time.
• The exit, I hope, will alternate unwisely.

EDIT I could just as well just keep ninja

the foreground calls (which is what I am currently doing), but then there would be no easy way to evaluate what is currently happening (the whole) assembly.

So, I would like to do one of the following:

• combine files build.ninja
  
  into one large file that can do both builds in one call ninja
  
  .
• run ninja
  
  with multiple target scripts build.ninja
  
  .

The second parameter doesn't seem to be supported ninja

, but the first seems like it can be done easily enough using subninja <build-dir-n>/build.ninja

. Has anyone done something like this before? Are there hidden pitfalls? Alternatively, I could just do the builds in sequence (i.e. the above sequence, but without &

s), but that doesn't seem like the right solution.

Register usage

I am using CMake

which generates a separate file build.ninja

for each build configuration (release and debug). I am targeting multiple platforms as well, so I have multiple compilers and CMake has to run separately for each platform. So if I want to build release and debug code for all platforms, I need to run ninja

multiple times.