Related: #1540549 - use the workaround for f28 only

... so that it does not break the build with old versions of GCC

curl.spec

@@ -158,9 +158,11 @@ be installed.
 
 # temporarily work around internal compiler error on x86_64 (#1540549)
 %ifarch x86_64
+%if 0%{?fedora} >= 28
 sed -e 's|-c -o tftpd-tftpd.o|-fcf-protection=none &|' \
     -i tests/server/Makefile.in
 %endif
+%endif
 
 # disable test 1112 (#565305) and test 1801
 # <https://github.com/bagder/curl/commit/21e82bd6#commitcomment-12226582>