Tie into `code_analysis`'s `get_clang_tools()` functionality to
intelligently bootstrap clang if it either doesn't exist or is
out-of-date.
This required exposing `command_context` to the linting logic, as it's
needed to call `artifact_toolchain(...)`.
Note that this means that the standalone `runcli.py` file won't be able
to support bootstrapping `clang-format`, or other linters that lean on
`command_context` in the future.
Finally, `substs.get("HOST_BIN_SUFFIX")` was replaced with a
windows-specific `binary += ".exe"`, because not all contexts where
the tests are run will have access to populated `substs` data.
Note that this worked before without the extension because it was
only used for starting a process, in which context Windows automatically
tries all `PATHEXT` options. Since we're now doing an `isfile()` check
(to enable more intelligent failure cases when `clang-format` doesn't
exist), we need the path to be fully correct.
Differential Revision: https://phabricator.services.mozilla.com/D137335
8c04017a04