Crash on Win7 startup due to BCryptGenRandom exception

[DuShijun]

Call stack:

• With MIMALLOC_DISABLE_REDIRECT=1:

• With MIMALLOC_DISABLE_REDIRECT=0:

[daanx]

:-(
One workaround is to define MI_USE_RTLGENRANDOM at build time; like cmake ../.. -DMI_EXTRA_CPPDEFS="MI_USE_RTLGENRANDOM=1". (see src/prim/windows/prim.c:607)