python3: fix do_install fail for parallel buiild

python3: fix do_install fail for parallel buiild

When using make -j with the 'install' target, it's possible for altbininstall
(which normally creates BINDIR) and libainstall (which doesn't, though it
installs python-config there) to race, resulting in a failure due to
attempting to install python-config into a nonexistent BINDIR. Ensure it also
exists in the libainstall target.

Signed-off-by: Changqing Li <changqing.li@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>