linkers: Accept both str and List[str] for _apply_prefix
linkers: Accept both str and List[str] for _apply_prefix

Simplifies some usage.

jpakkane/meson,QuLogic/meson,pexip/meson,pexip/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,becm/meson,becm/meson,QuLogic/meson,becm/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,becm/meson,jpakkane/meson,QuLogic/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,becm/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,pexip/meson,mesonbuild/meson,becm/meson,QuLogic/meson,becm/meson,jpakkane/meson,QuLogic/meson,pexip/meson,becm/meson,pexip/meson,QuLogic/meson,becm/meson,mesonbuild/meson,becm/meson,pexip/meson,pexip/meson,mesonbuild/meson,jpakkane/meson