feat(uucore): add shared hardware detection module

Add shared CPU hardware capability detection in uucore to prevent
code duplication across utilities. This provides a unified interface
for detecting CPU features (AVX512, AVX2, PCLMUL, SSE2, ASIMD) and
respecting GLIBC_TUNABLES environment variable.

This unblocks PR #9088 (cksum --debug) and PR #9144 (wc --debug) by
providing a common implementation that both utilities can use.

Features:
- CPU feature detection with caching (singleton pattern)
- GLIBC_TUNABLES parsing for hwcaps restrictions
- Cross-platform support (x86/x86_64, aarch64)
- Comprehensive test coverage
- Zero-cost abstractions using std::arch

Implementation details:
- Uses std::arch feature detection (no external deps for detection)
- Adds cfg-if dependency for conditional compilation
- Feature-gated behind "hardware" feature flag
- Android excluded (no CPUID access in sandboxed environment)

Related: #9088, #9144

Author: naoNao89

Cargo.lock

@@ -302,6 +302,7 @@ binary-heap-plus = "0.5.0"
 bstr = "1.9.1"
 bytecount = "0.6.8"
 byteorder = "1.5.0"
+cfg-if = "1.0"
 chrono = { version = "0.4.41", default-features = false, features = [
   "std",
   "alloc",

Cargo.toml

@@ -23,6 +23,7 @@ path = "src/lib/lib.rs"
 
 [dependencies]
 bstr = { workspace = true }
+cfg-if = { workspace = true }
 chrono = { workspace = true, optional = true }
 clap = { workspace = true }
 uucore_procs = { workspace = true }
@@ -131,6 +132,7 @@ fast-inc = []
 fs = ["dunce", "libc", "winapi-util", "windows-sys"]
 fsext = ["libc", "windows-sys"]
 fsxattr = ["xattr"]
+hardware = []
 lines = []
 feat_systemd_logind = ["utmpx", "libc"]
 format = [

src/uucore/Cargo.toml

@@ -74,6 +74,8 @@ pub mod tty;
 
 #[cfg(all(unix, feature = "fsxattr"))]
 pub mod fsxattr;
+#[cfg(feature = "hardware")]
+pub mod hardware;
 #[cfg(all(target_os = "linux", feature = "selinux"))]
 pub mod selinux;
 #[cfg(all(unix, not(target_os = "fuchsia"), feature = "signals"))]