lz4: pass {TARGET,HOST}_CONFIGURE_OPTS in the environment

lz4: pass {TARGET,HOST}_CONFIGURE_OPTS in the environment

{TARGET,HOST}_CONFIGURE_OPTS are currently passed as $(MAKE) argument,
which causes some CPPFLAGS/CFLAGS defined by the package build system to
be overridden, leading to build failures. This commit changes the lz4
package to pass {TARGET,HOST}_CONFIGURE_OPTS through the environment to
avoid this issue.

Fixes:

  http://autobuild.buildroot.net/results/2a578a9c462463fde802c999156723494fe1b14d/

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