package/uboot-tools: resolve host uboot env/script error

package/uboot-tools: resolve host uboot env/script error

The host build of uboot-tools can occur early in the build process and may
require the creation of BINARIES_DIR before generation of an enabled envimage
and/or boot script binary. So to resolve this in proper way, separated the
build and installation part of uboot env/script in their respective commands.

Signed-off-by: Kalpesh Panchal <kalpesh.panchal@rockwellcollins.com>
Signed-off-by: Matt Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>