We should document what external dependencies we assume for our test suites

[jieyouxu]

Location

The test suites, especially tests/run-make and tests/run-make-fulldeps.

Summary

It'd be nice for people to be able to reliably run test suites without necessarily having to rely on Docker environments, or at least know what external dependencies are assumed to be available (and what version/flavor as well) by the test suites. This is also relevant for people trying to work on or maintain new targets if they want to run the test suites. Example dependencies (non-exhaustive, have not fully surveyed):

• Utilities: e.g. nm, grep.
• C/C++ compilers, e.g. what cc points to is a massive pain.
• Python: again, which python version is also a massive pain.
• Make and makefiles: we're trying to escape from this
• Shell: bash? or what do the various bash scripts assume?

For example, the run-make test suite has a bunch of assumed external dependencies (like nm) which are not documented AFAICT.

[lolbinarycat]

src/tools/run-make-support/src/external_deps/ would be a good place to start.