Pipelines takes an enormous amount of time to compile C++ code during a docker build

[Robert Dailey]

I have a pipelines build running, and all it does is `docker build`. Inside the `Dockerfile` of that build, it is compiling a C++ library to store the final output binaries in the image for usage later. However, the C++ build is extremely slow. About 12 minutes have gone by and it only compiled 1 file. This is eating up the precious minutes I pay for. Why is this so slow?

[Robert Dailey]

After poking around a bit, I think it has to do with how many processes are simultaneously compiling translation units during the docker build. Basically you have to do `make -j4` to limit it. 4 works, 8 threads hangs it.