self-hosted: remove `zig libc` command for now
self-hosted: remove `zig libc` command for now

Since it depends on the C++ Windows SDK code. For now, self-hosted is
staying pure self hosted, no C/C++ components.

andrewrk/zig,zig-lang/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,andrewrk/zig