main/s390-tools: disable _FORTIFY_SOURCE in zipl
Disabling _FORTIFY_SOURCE fixes SIGFPE in zipl:
Program received signal SIGFPE, Arithmetic exception. memcpy (__n=7976, __os=, __od=0x3fffdff60c0) at /usr/include/fortify/string.h:53 53 return __builtin_memcpy(__od, __os, __n);
disassebly shows that the exception happens on the jump instruction to memcpy. Work around it by disabling _FORTIFY_SOURCE for zipl.
(cherry picked from commit 9fa93539)