buildroot

pkg-cmake: move configuration files out of $(HOST_DIR)/usr

Move toolchainfile.cmake and Buildroot.cmake from
$(HOST_DIR)/usr/share/buildroot to $(HOST_DIR)/share/buildroot.

Build-tested with a bunch of cmake packages.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>