[Fake.Tools.Signtool] x86 v. x64 versions of signtool.exe

[Numpsy]

I've been using the Signtool module at work to sign some libraries for a while, and it's been working ok.

However, there are some changes to the way things work in progress, and that has apparently hit an issue in that the way it's set up requires the use of a 64bit/x64 version of signtool.exe, and the fake module is only looking in the 'x86' folder - https://github.com/fsprojects/FAKE/blob/master/src/app/Fake.Tools.SignTool/SignTool.fs#L358 - and the x64 versions are under {Environment.ProgramFilesX86}\Windows Kits\10\bin\**\x64" (note: they're still under the ProgramFilesX86 root, just in a different sub directory)

It works if I work out the path myself and pass that into FAKE rather than letting it work it out, but I thought it would be nice if something could be done to let it work automatically.

I had a quick go with a custom build that adds a new 'prefer 64bit option' in Numpsy@43a4679 and that has worked for me, but I don't know if that would work for an 'official' change... I'm thinking that simply changing it to use the x64 version on 64bit platforms all the time has scope for breaking something, so an explicit flag is safer.

[xperiandri]

Maybe x86 must be opt-in, but x64 by default?

[Numpsy]

I wondered whether it could default to matching the bitness of the parent process and then allow that to be overridden (i.e. if Environment.Is64BitProcess is true then default to the x64 version if present, otherwise use the x86 version)

I think it does need an override option though, as an escape hatch in case someone needs to force a certain architecture

[Numpsy]

Maybe x86 must be opt-in, but x64 by default?

So would it be ok to make it default to the x64 version of signtool by default if the build process is 64bit, but then have some sort of optional flag to force the x86/x64 version as an escape hatch?

I think the 64bit default would still need to fall back to the 32bit version if there was no 64bit exe available, given that the exe is installed by the Windows SDK and you might not have the 64bit version installed.