osmo-auc-gen: Fix compiler warnings about aliasing

I ran "./utils/osmo-auc-gen -2 -a COMP128v1" and verified that
the RAND doen't look empty

Fixes:
osmo-auc-gen.c: In function ‘main’:
osmo-auc-gen.c:219:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   *(uint32_t *)&_rand[0] = rand();
   ^
osmo-auc-gen.c:220:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   *(uint32_t *)(&_rand[4]) = rand();
   ^
osmo-auc-gen.c:221:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   *(uint32_t *)(&_rand[8]) = rand();
   ^
osmo-auc-gen.c:222:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   *(uint32_t *)(&_rand[12]) = rand();
1 file changed