/usr/lib64/libcups.so.2 in cups-libs-2.2.6-7.fc29.x86_64.rpm was not linked with the standard Fedora linker flags (LDFLAGS) from redhat-rpm-config:

cc  -L../cups  -Wl,-soname,`basename libcups.so.2` -shared -Wall -Wno-format-y2k -Wunused -fPIC -g -fstack-protector -Wno-unused-result -Wsign-conversion -Wno-tautological-compare -Wno-format-truncation -D_GNU_SOURCE -o libcups.so.2 adminutil.o array.o auth.o backchannel.o backend.o debug.o dest.o dest-job.o dest-localization.o dest-options.o dir.o encode.o file.o getdevices.o getifaddrs.o getputfile.o globals.o hash.o http.o http-addr.o http-addrlist.o http-support.o ipp.o ipp-support.o langprintf.o language.o md5.o md5passwd.o notify.o options.o ppd.o ppd-attr.o ppd-cache.o ppd-conflicts.o ppd-custom.o ppd-emit.o ppd-localize.o ppd-mark.o ppd-page.o ppd-util.o pwg-media.o request.o sidechannel.o snmp.o snprintf.o string.o tempfile.o thread.o tls.o transcode.o usersys.o util.o -lgssapi_krb5 -lkrb5 -lk5crypto -lcom_err \
	-lgnutls  -lavahi-common -lavahi-client  -lpthread -lm -lcrypt   
/usr/bin/ar crvs libcups.a adminutil.o array.o auth.o backchannel.o backend.o debug.o dest.o dest-job.o dest-localization.o dest-options.o dir.o encode.o file.o getdevices.o getifaddrs.o getputfile.o globals.o hash.o http.o http-addr.o http-addrlist.o http-support.o ipp.o ipp-support.o langprintf.o language.o md5.o md5passwd.o notify.o options.o ppd.o ppd-attr.o ppd-cache.o ppd-conflicts.o ppd-custom.o ppd-emit.o ppd-localize.o ppd-mark.o ppd-page.o ppd-util.o pwg-media.o request.o sidechannel.o snmp.o snprintf.o string.o tempfile.o thread.o tls.o transcode.o usersys.o util.o

Looks like LDFLAGS are completely missing.

Please fix this in Fedora 28 as well.

See https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/master/f/buildflags.md for information on RPM macros and environment variables provided by the build environment.