print feature flags used for matching pkgimage (#50172)
```
julia> @ccall jl_dump_host_cpu()::Cvoid
CPU: znver2
Features: sse3, pclmul, ssse3, fma, cx16, sse4.1, sse4.2, movbe, popcnt, aes, xsave, avx, f16c, rdrnd, fsgsbase, bmi, avx2, bmi2, rdseed, adx, clflushopt, clwb, sha, rdpid, sahf, lzcnt, sse4a, prfchw, mwaitx, xsaveopt, xsavec, xsaves, clzero, wbnoinvd
julia> target = only(Base.current_image_targets())
znver2; flags=0; features_en=(sse3, pclmul, ssse3, fma, cx16, sse4.1, sse4.2, movbe, popcnt, aes, xsave, avx, f16c, fsgsbase, bmi, avx2, bmi2, adx, clflushopt, clwb, sha, rdpid, sahf, lzcnt, sse4a, prfchw, mwaitx, xsavec, xsaves, clzero, wbnoinvd)
```
Co-authored-by: Prem Chintalapudi <prem.chintalapudi@gmail.com>
Co-authored-by: Jameson Nash <vtjnash@gmail.com>
