complibs: fixup the host complibs install dir

It's easier to have as much as possible stuff in the same place to
ease backup/restore, and make things easier to follow.

Move the host companion libraries install dir as a sub-dir of the
build-tools install dir (but not directly in it, it would break
for canadian or cross-native).

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

 # Compute Blackfin-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="bfin"

     # gcc ./configure flags

     CT_ARCH_WITH_ARCH=

     CT_ARCH_WITH_ABI=

     CT_ARCH_WITH_CPU=

     CT_ARCH_WITH_TUNE=

     CT_ARCH_WITH_FPU=

     CT_ARCH_WITH_FLOAT=

 }