How to pass PROTOC environment variable to tonic-health?

[tamuhey]

Sample repository: https://github.com/tamuhey/bazel_tonic_sample

I want to use tonic-health crate, which uses protoc in its build.rs.
Now, bazel build is failing with the following error:

Error: Custom { kind: NotFound, error: "failed to invoke protoc (hint: https://docs.rs/prost-build/#sourcing-protoc): No such file or directory (os error 2)" }

This indicates build.rs couldn't find protoc.
I can pass the build if I manually edit BUILD.tonic-health.bazel which is generated by cargo-raze and add PROTOC env var and protoc data into :tonic_health_build_script, but I don't want to edit the machine-generated file.
And I know I can pass the protoc binary to the build environment with CrateSettings.data_dependencies.
However, I don't know how to set the binary path to PROTOC env var.
How to do that?

[GregBowyer]

This is not a good answer.

I am working on getting tonic to work with rules_proto_grpc as fairly out of the box. I might be messing with this and have a better answer when I am further down that road.

[redshirtrob]

Here's how I made this work:

[package.metadata.raze.crates.tonic-health.'*']
build_tools_dependencies = [
    "@//:protoc",
]

[package.metadata.raze.crates.tonic-health.'*'.buildrs_additional_environment_variables]
PROTOC = "$(location @//:protoc)"