I'm using libpopt in a little project of mine, and this popt.pc from the archlinux package does the job just fine. Please include it in the debian package.
--- begin popt.pc ---
prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include
Name: popt
Version: 1.16
Description: popt library.
Libs: -L${libdir} -lpopt
Cflags: -I${includedir}
--- end popt.pc ---
