MacOS sandboxing experiments

To run a Julia test, use make sandbox-FOO where FOO is the name of a valid argument to Base.runtests(). Good examples are all, cmdlineargs, InteractiveUtils, etc...

To compare against unsandboxed execution, run test-FOO.

Known issues:

With a few patches merged, this is now working as expected!

Workarounds in place:

The following tests have strange behavior that we should probably fix:

• cmdlineargs test requires writing to share/julia/test/testhelpers
• get_anon_hdl() ignores $TMPDIR, instead always writing to /tmp
• Profile looks up lineinfo data which uses paths embedded during build, so it requires read access to paths that most likely do not exist (e.g. /Users/julia/buildbot/worker/package_macos64/build).

Reading list:

• https://blog.squarelemon.com/2015/02/os-x-sandbox-quickstart/

• https://jmmv.dev/2019/11/macos-sandbox-exec.html

• https://reverse.put.as/wp-content/uploads/2011/09/Apple-Sandbox-Guide-v1.0.pdf