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