zeromq: fix build on m68k_cf

An internal compiler error is raised on m68k_cf at dwarf2cfi.c:2752 in
connect_traces. Error can be fixed by adding -fno-defer-pop, see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58864

Fixes:
 - http://autobuild.buildroot.net/results/dad241acbe59b1c5a24a0a2f3da6b12a553aec84



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>