Support a way to pass cache-irrelevant information to locally executed actions

[afq984]

Description of the feature request:

Add a build flag --local_action_env=KEY=VALUE which exposes the environment variable KEY=VALUE to build actions only if they are locally executed. Moreover the environment would not end up in the action key.

Which category does this issue belong to?

No response

What underlying problem are you trying to solve with this feature?

Our ChromeOS portage build wraps other build systems (somewhat like rules_foreign_cc) and would benefit from inter-action artifact caching. Our non-Bazel equivalent uses ccache to achieve that.

We would like to use the proposed --local_action_env to pass the path of the ccache directory (and possibly other configs) into the build action. The environment variable passed this way shouldn't end up in the action key because that would make remotely cached artifacts unusable. The environment variable also shouldn't be exposed to remotely executed actions because the local ccache directory path does not make sense to the remote executors.

Which operating system are you running Bazel on?

No response

What is the output of bazel info release?

No response

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

Internal discussion document and thread

Also thanks @lberki for this idea!

[tjgq]

What's the difference between this and #20950?

[afq984]

Oops, this is a dupe.