core/pkg-infrastructures: remove LD_LIBRARY_PATH from the environment

If system tools are selected, the host's lib/ directory may shadow
libraries from the system which are configured differently and do not
have all of the symbols required by the system tool.

Since buildroot now uses rpath everywhere, LD_LIBRARY_PATH should not
be necessary anyways.

Signed-off-by: Ben Boeckel <mathstuf@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>