#19 make check fails in testrsa on x86_64 alpine linux

[Natanael Copa]

make check fails in testrsa with Alpine Linux which uses musl libc. It looks like it is fortify that catches an overlapping memcpy which leads to undefined behavior:

Core was generated by `/home/ncopa/aports/main/beecrypt/src/beecrypt-4.2.1/tests/.libs/lt-testrsa'.
Program terminated with signal SIGILL, Illegal instruction.
#0  memcpy (__n=72, __os=0x72a36bd16328, __od=0x72a36bd162e8) at /usr/include/fortify/string.h:48
48                      __builtin_trap();
[Current thread is 1 (LWP 8493)]
(gdb) bt
#0  memcpy (__n=72, __os=0x72a36bd16328, __od=0x72a36bd162e8) at /usr/include/fortify/string.h:48
#1  mpndivmod (result=result@entry=0x72a36bd162e0, xsize=xsize@entry=9, xdata=xdata@entry=0x72a36bd16328, ysize=ysize@entry=4, ydata=0x3a05de82e40, 
    workspace=workspace@entry=0x72a36bd16370) at mp.c:1372
#2  0x000072a36c2a5ae6 in rsakpMake (kp=0x7a42bd0faff0, rgc=0x7a42bd0fafe0, bits=512) at rsakp.c:74
#3  0x000003a05bacbb8b in main () at testrsa.c:89