MessagePack ships both in a C++ and a C variant. Add the latter to Buildroot. This will be used by fluent-bit. Signed-off-by: Thomas Devoogdt <thomas@devoogdt.com> [Julien: - switch homepage URL to use https - add a note in package/msgpack{,-c}/Config.in to clarify C/C++ variants ] Signed-off-by: Julien Olivain <ju.o@free.fr>