package/sdbusplus: new package

package/sdbusplus: new package

A C++ library for interacting with sd-bus and a C++ bindings generator.

The host build produces a code generation tool, sdbus++ while the
target build gives libsdbusplus.

The code generator requires host-python-pyyaml, host-python-inflection,
and host-python-mako. Since it isn't built for the target, the target
build does not require them.

The host package includes a code and documentation generation program,
which is useful for including in a buildroot SDK, even if no target
package needs it, so make it a user-selectable host package.

host-autoconf-archive is added as a dependency since configure.ac
uses the AX_PKG_CHECK_MODULES macro.

Signed-off-by: John Faith <jfaith@impinj.com>
Signed-off-by: Trent Piepho <tpiepho@impinj.com>
[Thomas: use host-python3 when BR2_PACKAGE_PYTHON3=y]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>