[Bug target/68081] Cygwin GCC cannot compile program that uses __builtin_ia32_rdseed64_step

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68081

--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> ---
For intrinsics, gcc mostly considers Intel as the standard, so the
documentation would be https://software.intel.com/en-us/node/523865 .