cksum: Hardware detection fails to take GLIBC_TUNABLES env var into account #9518
Description
When trying to run the cksum.sh test, I realized that our implementation does not read GLIBC_TUNABLES.
Example:
(venv_pe) peron in ~/playground/coreutils on cksum-improvements λ GLIBC_TUNABLES='glibc.cpu.hwcaps=-AVX512F,-AVX2,-AVX,-PMULL' ../gnu/src/cksum --debug
cksum: avx512 support not detected
cksum: avx2 support not detected
cksum: pclmul support not detected
(venv_pe) peron in ~/playground/coreutils on cksum-improvements λ GLIBC_TUNABLES='glibc.cpu.hwcaps=-AVX512F,-AVX2,-AVX,-PMULL' ./target/debug/cksum --debug
cksum: avx512 support not detected
cksum: using avx2 hardware support
cksum: using pclmul hardware support
(venv_pe) peron in ~/playground/coreutils on cksum-improvements λ ./target/debug/cksum --debug
cksum: avx512 support not detected
cksum: using avx2 hardware support
cksum: using pclmul hardware support