Adding an embedded signature on setup-x86_64.exe

[Jon Turney]

On 20/11/2022 08:46, Thomas Wolff wrote:
>> In case we ever need it, one of our setup maintainers packaged 
>> osslsigncode:
>>
>>     https://cygwin.com/packages/summary/osslsigncode-src.html
>>
> Packaging error: the binary is placed in /usr

Thanks for pointing this out.

It seems this was an upstream defect in the cmake conversion they did in 
this version.  I applied the upstream patch to correct it.