Add slaveStr
Update .gitignore after all slaves are joined, not while they're still
updating it.

Also add a print about update of .gitignore.
Don't log about wait for slaves
TODO
Add Lib.{Fifo,PoolAlloc}
Use Parallelism pool instead of semaphore
Print why we pause executable
Inherit indent level from parent target's printer
Printer supports ByteString.Char8 printing
lines strips final \n, intercalate does not re-inject it, use putStrLn for STDOUT/STDERR printing