complibs: noone is using companion libs on the target; nuke them

As there's no longer any user of the companion libraries on the
target, nuke the build for the target.

Well, at least, there's libelf that's still needed by ltrace, so
we keep it.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Blackfin specific configuration file

config ARCH_blackfin

    select ARCH_SUPPORTS_32

    select ARCH_DEFAULT_32

    select ARCH_DEFAULT_LE

    select ARCH_SUPPORT_ARCH

    select ARCH_SUPPORT_CPU

    select ARCH_SUPPORT_TUNE

    select ARCH_SUPPORT_FPU

     help

      The Blackfin architecture