Auditor tries to dlopen libraries ignoring the march tag

[giordano]

At the moment the auditor tries to dlopen the library under this condition:

BinaryBuilder.jl/src/Auditor.jl

Line 140 in 3955444

if platforms_match(platform, HostPlatform())

but

julia> platform = HostPlatform()
Linux x86_64 {cxxstring_abi=cxx11, julia_version=1.7.2, libc=glibc, libgfortran_version=5.0.0, libstdcxx_version=3.4.29}

julia> platform["march"] = "avx512"
"avx512"

julia> platforms_match(platform, HostPlatform())
true

this means that HostPlatform() matches anything derived from HostPlatform() which differs only on the march tag, which is ignored. In particular this means we'll try to dlopen an AVX512 library on the build machine, but for example on Yggdrasil we don't have an AVX512-equipped system, so we get an illegal instruction error.

We need a custom comparison strategy for the march key, similarly to what we do for the os_version in Julia Base: https://github.com/JuliaLang/julia/blob/62e0729dbc5f9d5d93d14dcd49457f02a0c6d3a7/base/binaryplatforms.jl#L287-L317