feat(google/crc32c): add LLAR formula for crc32c 1.1.1+

[fennoai]

Translates the Conan Center crc32c recipe into an idiomatic LLAR Formula for google/crc32c. Closes #47.

What was added

• google/crc32c/versions.json — module metadata, no static deps.
• google/crc32c/1.1.1/Crc32c_llar.gox — the build formula.

Translation decisions (upstream-verified)

• fromVer "1.1.1" — the earliest version the Conan recipe folder serves. Upstream 1.1.1 and 1.1.2 share an identical build contract (same option() set, single installed header crc32c/crc32c.h, target crc32c, cmake_minimum_required(VERSION 3.1)), so one Formula covers both without an extra threshold.
• No dependencies / no onRequire — glog, googletest and benchmark are vendored subprojects used only by the tests/benchmarks, which are disabled. There are no find_package/requires deps.
• onBuild — CMake with CRC32C_BUILD_TESTS=OFF, CRC32C_BUILD_BENCHMARKS=OFF, CRC32C_USE_GLOG=OFF, CRC32C_INSTALL=ON (matching the recipe's generate block). CMAKE_POLICY_VERSION_MINIMUM=3.5 keeps the CMake-3.1 project buildable under CMake 4, mirroring the recipe's <= 1.1.2 handling. Metadata is -lcrc32c.
• onTest — compiles and runs a small consumer that mirrors the Conan test_package (raw-buffer and std::string overloads of crc32c::Crc32c) against the installed exported package target Crc32c::crc32c. Its build tree is independent of the onBuild _build dir, so it also passes on a cache hit.

Validation

Ran locally on linux/amd64 (only host arch available in the sandbox):

Selection	Result
llar test ./google/crc32c@1.1.2 --os linux --arch amd64 (exact Conan tag)	✅ build + install + consumer pass, -lcrc32c
llar test ./google/crc32c@1.1.1 --os linux --arch amd64 (fromVer boundary)	✅ pass
1.1.2 re-run (cache hit)	✅ onBuild skipped, onTest still passes

darwin and arm64 are not runnable in this sandbox; the repo's test.yml matrix covers all four platforms on PR. crc32c's CMake performs its own SSE4.2 / ARMv8-CRC feature detection, so no matrix options were needed.

[fennoai]

Review: google/crc32c 1.1.1 formula

Solid, well-commented formula. The build recipe, CMake option handling (CRC32C_BUILD_TESTS/BENCHMARKS/USE_GLOG=OFF, CRC32C_INSTALL=ON), -lcrc32c metadata, id/versions.json.path/directory alignment, fromVer "1.1.1" literal, and the Crc32c_llar.gox → Crc32c class-name stem all check out against the LLAR spec and the upstream crc32c 1.1.1 source. Inline comments were verified accurate against upstream (cmake 3.1 minimum, exported Crc32c::crc32c target, lib/cmake/Crc32c, no pkg-config file). No security concerns.

Two findings inline. The onTest one is worth addressing before merge; the other is minor cleanup.

Note: reviewed against the checked-out branch after fetching the PR head.

[fennoai]

onTest is effectively a tautology and does not validate CRC correctness. a = crc32c::Crc32c(buffer, 4) runs over 4 zero bytes, and b = crc32c::Crc32c(s) runs over a std::string of size 4 (default-filled with '\0'). The std::string overload just forwards the same bytes to the same routine, so a == b is guaranteed true by construction — the check passes even if Crc32c were broken (e.g. returned a constant), since it only proves the two overloads agree, not that the CRC is computed correctly.

Assert against a known-answer constant instead. CRC32C over 4 zero bytes is 0x48674BC7; e.g. return (a == 0x48674BC7u) ? 0 : 1; (optionally still checking a == b) turns this into a real smoke test that would catch a miscompiled/misconfigured library. A second vector such as "123456789" → 0xE3069283 would strengthen it further.

[fennoai]

Minor: CMAKE_POLICY_VERSION_MINIMUM=3.5 is redundant here. The generated consumer CMakeLists.txt already declares cmake_minimum_required(VERSION 3.5), and CMake config packages (loaded via find_package(Crc32c CONFIG)) don't call cmake_minimum_required, so this shim is dead in the test path. It is justified in onBuild (line 13) because upstream's own top-level CMakeLists.txt requests VERSION 3.1. Consider dropping it from onTest, or add a note explaining which downstream file it guards.