Rust bootstrap 1.60.0

Rust 1.60.0 bootstrap tarballs created using the standard Rust "dist" command. They depend only on musl.

They are for use by the glasnost build files to bootstrap the Rust build process.

Example ldd output for rustc:

$ ldd rustc
        /lib/ld-musl-x86_64.so.1 (0x7f39403a8000)
        librustc_driver-8b21ce809b9a09f1.so => ./../lib/librustc_driver-8b21ce809b9a09f1.so (0x7f39375f7000)
        libstd-6827a715857e4f5a.so => ./../lib/libstd-6827a715857e4f5a.so (0x7f39374f1000)
        libc.so => /lib/ld-musl-x86_64.so.1 (0x7f39403a8000)

Cargo:

$ ldd cargo
        /lib/ld-musl-x86_64.so.1 (0x7fb00868f000)
        libc.so => /lib/ld-musl-x86_64.so.1 (0x7fb00868f000)