musl bootstrap: remove libiconv

pkgs/stdenv/linux/bootstrap-tools-musl/scripts/unpack-bootstrap-tools.sh

···
         ./patchelf --set-interpreter $LD_BINARY --set-rpath $out/lib --force-rpath "$i"
 done
 
-for i in $out/lib/libiconv*.so $out/lib/libpcre* $out/lib/libc.so; do
+for i in $out/lib/libpcre* $out/lib/libc.so; do
     if [ -L "$i" ]; then continue; fi
     echo patching "$i"
     $out/bin/patchelf --set-rpath $out/lib --force-rpath "$i"

pkgs/stdenv/linux/make-bootstrap-tools.nix

···
         cp -d ${libmpc.out}/lib/libmpc*.so* $out/lib
         cp -d ${zlib.out}/lib/libz.so* $out/lib
         cp -d ${libelf}/lib/libelf.so* $out/lib
-      '' + lib.optionalString (hostPlatform.libc == "musl") ''
-        cp -d ${libiconv.out}/lib/libiconv*.so* $out/lib
 
       '' + lib.optionalString (hostPlatform != buildPlatform) ''
         # These needed for cross but not native tools because the stdenv