/usr/lib/cups/filter/rastertoqpdl and /usr/lib/cups/filter/pstoqpdl in splix-2.0.1-0.35.20130902svn.fc28.x86_64 have not been linked with the standard Fedora linker flags (LDFLAGS) from redhat-rpm-config:

g++ -o optimized/rastertoqpdl optimized/src/rastertoqpdl.o optimized/src/request.o optimized/src/printer.o optimized/src/qpdl.o optimized/src/document.o optimized/src/core.o optimized/src/compress.o optimized/src/algorithm.o optimized/src/ppdfile.o optimized/src/page.o optimized/src/colors.o optimized/src/band.o optimized/src/bandplane.o optimized/src/cache.o optimized/src/rendering.o optimized/src/semaphore.o optimized/src/algo0x0d.o optimized/src/algo0x0e.o optimized/src/algo0x11.o optimized/src/algo0x13.o optimized/src/algo0x15.o  `cups-config --ldflags` -L/opt/local/lib \
	`cups-config --libs` -lcupsimage -lpthread -ljbig85

g++ -o optimized/pstoqpdl optimized/src/pstoqpdl.o optimized/src/ppdfile.o  `cups-config --ldflags` \
	`cups-config --libs` -lcupsimage -lpthread

There is no LDFLAGS injection at all.  cups-config isn't very helpful:

# cups-config --ldflags

# cups-config --libs
-lcups -lgssapi_krb5 -lkrb5 -lk5crypto -lcom_err -lpthread -lm -lcrypt

(Hard-coding the build flags into cups-config wouldn't be advisable anyway.)