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.
Also expand the LIBS by upnpp_LIBS to set the necessary libraries for
linking with libupnpp. This fixes static build issues.
Signed-off-by: Jörg Krause joerg.krause@embedded.rocks
