Print directory change notifications around tool execution

[per-rtl]

Summary

• Print Entering directory '...' and Leaving directory '...' around tool invocations in _run_tool()
• Enables editors (Emacs, etc.) to resolve file paths in tool output when running from a build directory

Motivation

When edalize runs a tool (e.g. slang for linting), it sets cwd=self.work_root, so the tool reports file paths relative to the build directory. Editors that parse compiler output (like Emacs compilation-mode) cannot resolve these paths back to the source files.

GNU Make solved this with Entering directory / Leaving directory messages. This patch adds the same convention to edalize so that editor integrations work out of the box.

Test plan

• Run any edalize-backed tool (e.g. fusesoc run --target=slanglint ...)
• Verify Entering directory and Leaving directory appear in output
• Verify editor can resolve relative file paths in tool output to correct source locations

[olofk]

Looks good. Wondering if you want to enable the same for the Flow API backends too in edalize/tools/edatool.py

[per-rtl]

Looks good. Wondering if you want to enable the same for the Flow API backends too in edalize/tools/edatool.py

Seems like we should, will look into it.