IIUC, libc are not prebuilt and bundled ("for every supported target combination"), "just" the source code of musl and glibc is bundled, and compiled lazily on

IIUC, libc are not prebuilt and bundled ("for every supported target combination"), "just" the source code of musl and glibc is bundled, and compiled lazily on your machine when first needed (i.e. for any target for which you invoke zig).