Comment by jcupitt

sharp does not rebuild libvips, it downloads a pre-compiled libvips for your platform.

https://sharp.pixelplumbing.com/install/#prebuilt-binaries

It can usually also download a precompiled binary for the C++ shim that sits between node and libvips, but if your node / arch / etc. is not supported, it'll compile that (that's what the build.js file you linked does).