% readelf -d $(where cat)

Dynamic section at offset 0x13b080 contains 32 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libcrypto.so.3]
 0x0000000000000001 (NEEDED)             Shared library: [libacl.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libattr.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libgmp.so.10]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x000000000000001d (RUNPATH)            Library runpath: [/nix/store/wah0xp4ani8b4l7d6hcjlb2lyiy2g83z-acl-2.3.1/lib:/nix/store/d0v43l0kfszyiq8ln9mgizg3yyp63p81-attr-2.5.1/lib:/nix/store/kh108jif43dm3yk6yxr9zmyskybcww3w-gmp-with-cxx-6.2.1/lib:/nix/store/z963s748p2pxlv91q3lsm7hx3m06h0a9-openssl-3.0.9/lib:/nix/store/ibp4camsx1mlllwzh32yyqcq2r2xsy1a-glibc-2.37-8/lib]
 0x000000000000000c (INIT)               0x408000
 0x000000000000000d (FINI)               0x4dd814
 0x0000000000000019 (INIT_ARRAY)         0x531ff0
 0x000000000000001b (INIT_ARRAYSZ)       8 (bytes)
 0x000000000000001a (FINI_ARRAY)         0x531ff8
 0x000000000000001c (FINI_ARRAYSZ)       8 (bytes)
 0x0000000000000004 (HASH)               0x4003f8
 0x000000006ffffef5 (GNU_HASH)           0x400e98
 0x0000000000000005 (STRTAB)             0x4035e0
 0x0000000000000006 (SYMTAB)             0x400ef8
 0x000000000000000a (STRSZ)              5023 (bytes)
 0x000000000000000b (SYMENT)             24 (bytes)
 0x0000000000000015 (DEBUG)              0x0
 0x0000000000000003 (PLTGOT)             0x53c2d0
 0x0000000000000002 (PLTRELSZ)           9192 (bytes)
 0x0000000000000014 (PLTREL)             RELA
 0x0000000000000017 (JMPREL)             0x4050d8
 0x0000000000000007 (RELA)               0x404e80
 0x0000000000000008 (RELASZ)             600 (bytes)
 0x0000000000000009 (RELAENT)            24 (bytes)
 0x000000000000001e (FLAGS)              BIND_NOW
 0x000000006ffffffb (FLAGS_1)            Flags: NOW
 0x000000006ffffffe (VERNEED)            0x404cc0
 0x000000006fffffff (VERNEEDNUM)         4
 0x000000006ffffff0 (VERSYM)             0x404980
 0x0000000000000000 (NULL)               0x0

In Linux ld.so itself has a default directory it loads libc from:

$ ld.so --help
...
Shared library search path:
  (libraries located via /nix/store/ibp4camsx1mlllwzh32yyqcq2r2xsy1a-glibc-2.37-8/etc/ld.so.cache)
  /nix/store/ibp4camsx1mlllwzh32yyqcq2r2xsy1a-glibc-2.37-8/lib (system search path)
  /nix/store/5cfwfnp4capzbjmkkrl7a6shvaghgj3h-xgcc-12.3.0-libgcc/lib (system search path)

For example linux does it via steps like https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/linux/default.nix#L412:

  (prevStage:
    stageFun prevStage {
    name = "bootstrap-stage2";
    # ...
    overrides = self: super: {
      inherit (prevStage)
        ccWrapperStdenv gettext
        gcc-unwrapped coreutils gnugrep
        perl gnum4 bison texinfo which;

Here perl and friends come from a previous instance of stdenv instead of being built normally.

In reply to @snektron:matrix.org
And it looks like starfive finally added pci support in uboot

it's in ld-wrapper: pkgs/build-support/bintools-wrapper/ld-wrapper.sh:

        for path in "$dir"/*; do
            file="${path##*/}"
            if [ "${libs[$file]:-}" ]; then
                rpaths["$dir"]=1
                extraAfter+=(-rpath "$dir")
                break
            fi
        done

I believe dynamic linker is set inf a slightly different way: via nix-support/ld-set-dynamic-linker file indirection. From pkgs/build-support/bintools-wrapper/add-flags.sh:

if [ -z "$NIX_DYNAMIC_LINKER_@suffixSalt@" ] && [ -e @out@/nix-support/ld-set-dynamic-linker ]; then
    NIX_DYNAMIC_LINKER_@suffixSalt@="$(< @out@/nix-support/dynamic-linker)"
fi

and later in ld-wrapper: pkgs/build-support/bintools-wrapper/ld-wrapper.sh:

extraBefore+=("-dynamic-linker" "$NIX_DYNAMIC_LINKER_@suffixSalt@")