Expose BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN through a flag

[tpudlik]

Description of the feature request:

To ensure Bazel uses only hermetic, vendored C++ toolchains, and does not attempt to configure a local toolchain, you need to set the environment variable BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN.

This is not very ergonomic: it would be better to expose this option through a flag, so it can be set via .bazelrc alongside other configuration options.

In general, is there some guidance on when Bazel configuration options should be set via flags vs via environment variables?

Which category does this issue belong to?

C++/Objective-C Rules

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

No response

Which operating system are you running Bazel on?

Linux

What is the output of bazel info release?

release 6.3.2

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 master; 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?

No response

[benjaminp]

You can do --repo_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1.

[tpudlik]

Ah, I didn't know about the --repo_env flag!

But per the documentation, the variables specified by that flag are "available only for repository rules". So I don't think this will actually affect what cc_configure.bzl does.

[benjaminp]

But per the documentation, the variables specified by that flag are "available only for repository rules". So I don't think this will actually affect what cc_configure.bzl does.

The linked line is inside the cc_autoconf_toolchains repository rule.

[tpudlik]

D'uh, good point. Thank you for the explanation!