Extract the compile DB in the configuration we develop in

[helly25]

Fixes the root cause that #279 treats symptomatically, and closes the last coverage hole in compile_commands.json.

Depends on helly25/bazel-compile-commands-extractor#30 conceptually (see Dropping the repo alias below), but does not need it merged — the alias is simply removed here.

The root cause

The DB was extracted in the default build configuration and only had its compiler substituted afterwards via --bcce-compiler. Every other flag — standard library, include paths, feature macros — came from whatever toolchain bazel picked by default, which differs per platform. That is what made clang-tidy report differently on macOS and Linux.

Now it extracts with --config=clang-tidy, a new .bazelrc config:

common:clang-tidy --config=clang
common:clang-tidy --cxxopt=-stdlib=libc++
common:clang-tidy --linkopt=-stdlib=libc++

The stdlib stays explicit on purpose: development targets libc++, so the DB should say so rather than inherit the driver default (libc++ on macOS, libstdc++ on Linux).

Consequently --bcce-compiler is now redundant — the extracted commands already name the hermetic toolchain — and is dropped, along with the ~34-line compiler-resolution block that supported it. --bcce-copt=-isysroot stays: macOS still needs the SDK for system C headers.

The missing sources

aquery expands //... with manual targets already removed, so the benchmarks, the differential test and show_compiler were never in the DB at all — they were being linted with flags interpolated from unrelated siblings. //bazelmod:refresh_compile_commands now names them explicitly.

It is a single targets entry: the key is interpolated into deps(...), so it may be a query expression, and a union avoids duplicating flags per target.

targets = {" + ".join(["@//..."] + CLANG_TIDY_MANUAL_TARGETS): "--config=clang-tidy"}

A tag alone cannot do this job — aquery's manual exclusion happens before any attr(tags, ...) filter can see the target, which I confirmed returns nothing extra. So the clang-tidy tag states the intent, and a new clang-tidy-targets-match-tag hook fails if the tag and the explicit list ever disagree. Verified it detects a removed entry and names exactly which target drifted.

The one repository source still absent, mbo/hash/measurements/smhasher3/mbohash.cpp, cannot be included: it is an SMHasher3 plugin, copied into that project by build_smhasher3.sh and compiled by its cmake. There is no BUILD file for it here, and linting it against these flags would only produce bogus errors for the Platform.h / Hashlib.h it includes.

Dropping the repo alias

bazel_dep(..., repo_name = "bazel_compile_commands_extractor") is removed. The extractor's macro emits a raw @hedron_compile_commands//:print_args label, which resolves in the caller's repo context and so fails under a rename. Fixed upstream in helly25/bazel-compile-commands-extractor#30 (with a regression test); removing the alias here is the local unblock and nothing else referenced it.

Test

• compile_commands.json: 2034 entries, hermetic compiler, -stdlib=libc++ present, -isysroot retained, and every bazel-built source covered (was 6 missing).
• clang-tidy works with the extracted commands, including on the previously-missing hash_benchmark.cc.
• bazel test --config=clang //... — 109/109 pass.
• pre-commit run -a green, including the new drift check.