Fix netcore build with workaround

[enricosada]

apply workaround: Move fsproj for preview3 in another directory.

[enricosada]

annoying. locally build ok if you use preview3.

I'll leave there, because i cannot fix it tonight, maybe you can do it @forki

I tested locally the error.
on my local was working if i have preview3 in PATH
and fail with preview2 in PATH, same error.
I think that's because you are just running dotnetcore/dotnet.exe in FAKE script instead of adding dotnetcore dir to PATH env var before calling dotnet build.
Like that, in the target file, when i run dotnet compile-fsc is going to use the dotnet in PATH (pretty sure is preview2, so doesnt find compile-fsc) instead of the one inside dotnetcore (the preview3).

.net core sdk require dotnet sdk directory in PATH, that's how things works atm to resolve correct dotnet.exe. directly invoking dotnet.exe is not enough (there is also a discussion about that in FAKE)

[enricosada]

tried the proposed fix, let's see

[forki]

cool thanks