`bazel test` should exclude all blacklisted extensions/dependencies

[achasveachas]

Title: bazel test should exclude all blacklisted extensions/dependencies

Description:
Currently we are excluding blacklisted dependencies using the logic in extensions_build_system.bzl, the functions in this file get invoked in the individual BUILD files and they get mad if the excluded extension doesn't exist in EXTENSIONS (which should have been WINDOWS_EXTENSIONS in the windows case), and excluding PPC_SKIP_TARGETS and NOBORINGSSL_SKIP_TARGETS` in those cases.

Ideally we would want to construct a unified EXTENSIONS based on blacklists well before evaluating the BUILD files.

[optional Relevant Links:]
Slack Discussion

CC: @wrowe @lizan

[lizan]

Here is some pointer:

We do load default envoy_config here to provide @envoy_build_config//:extensions_build_config.bzl which defaults to @envoy//source/extensions:extensions_build_config.bzl. With the repository_ctx there you can conditionally load different bzl files as extensions_build_config.bzl. See _is_linux function in repositories.bzl.

@wrowe @achasveachas Do you want to take a stab?

[stale]

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[wrowe]

Note our confusion spawned from the following;

$ bazel test //test/...

This will build all tests, as pointed out by lizan during a community meeting.

Can you help us identify the "top level test" we should be invoking to observe all included and
excluded //source/... elements given the desired target //source/exe:envoy-static

[wrowe]

Ping @lizan

We understand that one top level test that can be performed is;
//test/exe:envoy-static

What we remain unclear on is what is the typical top-level test-all target which can be expected to run for only included and none of the excluded extensions, etc?

[lizan]

I guess the issue is some integration test is not using extension_cc_test but actually relying on extensions. I think we need refactor envoy_cc_test a bit to specify a list of extensions that the test requires, and no-op them if extensions doesn't exist.

[wrowe]

Confirming that this remains a sore point, we killed off WINDOWS_EXTENSIONS, but the extension_cc_test is still not looking at the platform's /exclusion/ list.