What you are missing is that for that platform the internal linker and assembler will just work. Don't need to specify an internal linker or assembler.
What you DO have to do is maybe set some options that are linux specific. like maybe -fPIC and -Tlinux
If you want to use un external linker anyway, the options are -FL\path\to\the\linker\ld (capital L, not lowercase l, not -Fl) , use -XP<x> for the binutilsprefix and -FD<binutils path>