buildroot

package/upmpdcli: add patch to use pkg-config for libupnpp

Building upmpdcli aborts because of an unsafe header inclusion of
`/usr/include/libupnpp`. Using `{prefix}` to get the header path is
wrong for cross-compilation.

Instead of hard-coding the flags for libupnpp use pkg-config to get the
correct ones.

Note that this patch adds the host-pkgconfig dependency unconditionally and
removes the necessity to pass the libupnpp manually to LIBS for a static
build.

Upstream-status: https://github.com/medoc92/upmpdcli/pull/49

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>