more cowbell for make

[eruditej]

change to make -j4 as the default, people might not know to change this themselves. It's 2018. They have at least 2 cores.

[kahiroka]

Thank you for your feedback.

[meisterplanlos]

Actually you should make this parameter dependent on the number of cores you have. The general rule is numcores+1 (+1 for IO operations). You can achieve this by using -j=$(($(nproc)+1)) instead of -j4

[kahiroka]

Thank you. Your idea was incorporated at abfa3e1.