Export some more symbols for libgoogle-cloud

[h-vetinari]

Trying to address failures in conda-forge/google-cloud-cpp-feedstock#196

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found it was in an excellent condition.

I do have some suggestions for making it better though...

For recipe/meta.yaml:

• ℹ️ The recipe is not parsable by parser conda-souschef (grayskull). This parser is not currently used by conda-forge, but may be in the future. We are collecting information to see which recipes are compatible with grayskull.
• ℹ️ The recipe is not parsable by parser conda-recipe-manager. The recipe can only be automatically migrated to the new v1 format if it is parseable by conda-recipe-manager.
• ℹ️ grpcio-tools output has some malformed specs:

• In section host: `grpcio =1.71.0=*_PKG_BUILDNUM
• In section run: grpcio =1.71.0=*_PKG_BUILDNUM Requirement spec fields should always be space-separated to avoid known issues in conda-build. For example, instead of name =version=build, use name version.* build`.

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/13853751292. Examine the logs at this URL for more detail.}

[conda-forge-admin]

Hi! This is the friendly conda-forge automerge bot!

I considered the following status checks when analyzing this PR:

• linter: passed
• azure: failed

Thus the PR was not passing and not merged.

[conda-forge-admin]

Hi! This is the friendly conda-forge automerge bot!

Commits were made to this PR after the automerge label was added. For security reasons, I have disabled automerge by removing the automerge label. Please add the automerge label again (or ask a maintainer to do so) if you'd like to enable automerge again!

[h-vetinari]

I had actually checked if the templated functions are somehow part of the symbols being skipped here, but CallbackUnaryCall is part of grpc++, not grpc.