Uses bazel 8 flags since there's the update in #4729. bazelisk was used
to generate the list of flags (see bazelrc comment). The overall
approach is trying to do our best to follow
https://bazel.build/release/backward-compatibility, in particular since
`--incompatible_strict_action_env` had come up (essentially just
adopting as much as we can now).
The default visibility changes in `carbon_rules/BUILD` and
`cc_toolchains/BUILD` files are for
`--incompatible_config_setting_private_default_visibility`. That's
enough for fastbuild, but we use tcmalloc in opt, and it has an issue.
In `clang_toolchain.BUILD` it's for
`--incompatible_check_visibility_for_toolchains`, even though
`rules_shell` then breaks on it. `manifest/defs.bzl` changes are for
`--incompatible_disable_target_default_provider_fields` which
`rules_pkg` breaks on. Even though these flags are off, I'm keeping the
changes since we should eventually enable the flags.
I'm still looking at the tree sitter rules due to the WORKSPACE issue,
but I think that needs more substantial work.
LLVM_SYMBOLIZER_PATH is required if `llvm-symbolizer` isn't in the developer's PATH. This sets it via bazel instead of having a developer handle it. I noticed this because the apt install of clang doesn't put llvm-symbolizer in the PATH.
I'd like to make this the default without putting it everywhere, but I don't see a way to do this intrinsically through [the toolchain](https://bazel.build/docs/cc-toolchain-config-reference), and the [rules_cc/defs.bzl](https://github.com/bazelbuild/rules_cc/blob/main/cc/defs.bzl) remains a thin wrapper around the native cc_binary.
Since I'm adding another env, it seems undesirable to have the macos asan workaround separate. As a consequence, this merges it in. Note bazel doesn't support merging a dict and a select, so it's also necessary to have the two env vars at least mildly aware there's something up (and this could get worse if we end up having more selects).
The Bazel bits are collected into a directory and given less confusing
names (I hope). Other than names, everything is a direct copy from the
toolchain repository without any edits.
A few files needed to be merged in:
- `.gitignore`
- `.pre-commit-config.yaml`
Subsequent commits will add relevant C++ infrastructure and then the
source code itself.
Jon Ross-Perkins
Chandler Carruth