OpenBSD does not have an rt library.

--- lib/libv4lconvert/libv4lconvert.pc.in.orig	Sat Jan 23 04:40:50 2016
+++ lib/libv4lconvert/libv4lconvert.pc.in	Sat Jan 23 04:40:58 2016
@@ -7,5 +7,5 @@ Name: libv4lconvert
 Description: v4l format conversion library
 Version: @PACKAGE_VERSION@
 Libs: -L${libdir} -lv4lconvert
-Libs.private: -lrt -lm @JPEG_LIBS@
+Libs.private: -lm @JPEG_LIBS@
 Cflags: -I${includedir}