[DO NO REVIEW] bazel: local OpenROAD with bazel-orfs

[oharboe]

@hzeller @maliberty Once OpenROAD uses MODULE.bazel, I'll be able to switch ORFS to use the locally checked out OpenROAD instead of the OpenROAD from the docker image in ORFS bazel-orfs targets:

The workflow locally run build ORFS test designs then becomes:

1. Modify tools/OpenROAD
2. cd flow/
3. bazel build ...

bazel-orfs needs to grow a capability so that ORFS, a user of bazel-orfs, can set "_openroad" to point to another label:

https://github.com/The-OpenROAD-Project/bazel-orfs/blob/a2e6a3a37693e3ab4c0459d508c08c3c667d2809/openroad.bzl#L384-L390

[oharboe]

Once https://github.com/The-OpenROAD-Project/OpenROAD/blob/master/WORKSPACE is fully converted to MODULE.bazel, my expectation is that the below will work.

Then bazel-orfs can be updated to have an option to configure @openroad//:openroad and use the locally checked out and built ORFS/tools/OpenROAD instead of being hardcoded to use the OpenROAD from the docker image https://github.com/The-OpenROAD-Project/bazel-orfs/blob/a2e6a3a37693e3ab4c0459d508c08c3c667d2809/openroad.bzl#L384-L390

$ bazel build @openroad//:openroad
WARNING: Target pattern parsing failed.
ERROR: Skipping '@openroad//:openroad': error loading package '@@openroad~//': Unable to find package for @@[unknown repo 'rules_hdl' requested from @@openroad~]//dependency_support/com_github_westes_flex:flex.bzl: The repository '@@[unknown repo 'rules_hdl' requested from @@openroad~]' could not be resolved: No repository visible as '@rules_hdl' from repository '@@openroad~'.
ERROR: error loading package '@@openroad~//': Unable to find package for @@[unknown repo 'rules_hdl' requested from @@openroad~]//dependency_support/com_github_westes_flex:flex.bzl: The repository '@@[unknown repo 'rules_hdl' requested from @@openroad~]' could not be resolved: No repository visible as '@rules_hdl' from repository '@@openroad~'.
INFO: Elapsed time: 0.066s
INFO: 0 processes.
ERROR: Build did NOT complete successfully

[oharboe]

@maliberty @hzeller out of sight and out of mind until OpenROAD is completely converted to MODULE.bazel and WORKSPACE is empty.