pwntools depends on binutils in order to perform assembly and disassembly of various architectures.
This is a repository of binutils installation scripts for various operating systems, specifically for cross-installations (e.g. assembling VAX on macOS).
Select the directory that corresponds to your operating system, and run install.sh. If you're curious or want to audit our methodology files used by install.sh are generated with generate.sh.
NOTE: As of Ubuntu 16.04 (Xenial), there are packages for most architectures available directly form Ubuntu.
You should just be able toapt-get install binutils-arm-gnueabihf binutils-mipsel-linux-gnu.
The Ubuntu installation process uses a Personal Package Archive (PPA) hosted by Ubuntu's Launchpad. These work by modifying a single binutils-cross .deb source archive, and changing the architecture.
No source code is changed, as the binutils-cross targets rely on the binutils-source package being installed, which is completely separate.
The builds are performed by Ubuntu, on Ubuntu's servers, against digitally signed source changes uploaded by pwntools maintainers.
The macOS installation process uses the homebrew package manager to build binutils from source.
The scripts generated are based on the original binutils recipe used by homebrew.
The binaries are built on your machine, with source fetched directly from the gnu.org server.