4th: create /usr/lib and /usr/bin before installation

4th: create /usr/lib and /usr/bin before installation

The 4th build system doesn't create the installation directories by
itself, causing $(HOST_DIR)/usr/lib to be a file containing the 4th
library if $(HOST_DIR)/usr/lib doesn't already exist as a
directory. Since 4th is the first package in the build order due to
alphabetic ordering, it is very likely that it will install a file as
$(HOST_DIR)/usr/lib, breaking the build of follow-up packages.

Fixes:

  http://autobuild.buildroot.net/results/6291046ca0552e11b79a84df4a7844324d78ab97/
  http://autobuild.buildroot.net/results/252642b7d6ec3f77142dcbd158f56ed8e2426c25/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>