Make build.sh executable via post-action

[rmunn]

See https://github.com/dotnet/templating/wiki/Post-Action-Registry#change-file-permissions for details. This should fix #19.

[TheAngryByrd]

🎸

[TheAngryByrd]

@rmunn just released 0.4.1-beta002 if you want to test it out

[rmunn]

Tried out 0.4.1-beta002 by downloading the NuGet package manually and then running dotnet new -i /home/rmunn/Downloads/miniscaffold.0.4.1-beta002.nupkg. (I couldn't figure out how to get dotnet new to give me prerelease NuGets; running dotnet new -i "MiniScaffold::*" just gave me 0.4.0). It opened up with an executable build.sh file. Had a different problem, which I also encountered with 0.4.0, where the FAKE package didn't get restored so build.sh failed — but I'll open a separate bug report for that one. As far as the post-install script goes, it works.

And BTW, if anyone tries to install this via dotnet new on .Net Core versions before 2.0.0, they won't get an exectuable build.sh script (because that particular post-action was introduced in .Net Core 2.0.0), but they will see the "Run 'chmod +x *.sh'" text associated with that post-action. Props to the .Net Core team for thinking through how that would work and putting forward-compatibility into their post-action system.

[TheAngryByrd]

I think if you give it the "exact" version. ``dotnet new -i MiniScaffold::0.4.1-beta002`

[TheAngryByrd]

Also I'll make a note in the readme about it! Thanks!

[rmunn]

Apparently the condition should have been "(OS != \"Windows_NT\")" (see dotnet/templating#1421 (comment)). I've opened PR #51 to fix that mistake.