limit build parallelism to 4 on a 32-bit machine
limit build parallelism to 4 on a 32-bit machine

 Merge to 5.1.2

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket