Support x86_64-musl as a host architecture

[farcaller]

Now that #55163 is closed this bug will serve as an aggregate for musl host architecture support. The known blockers are:

• static-pie for musl target (remove crt1.o) #53968

[mati865]

rustup toolchain install nightly-x86_64-unknown-linux-musl works now but it's not useful on most of glibc based distros unless you have unwinder built with musl.
There is WIP PR for musl built rustup which will run on musl based distros.