Could not resolve coreclr path

My project.json file looks like below:

{
    "version": "0.0.0",
    "compilationOptions": {
        "emitEntryPoint": true
    },
    "dependencies": {
        "BonVoyage": "*"
    },
    "frameworks": {
        "netcoreapp1.0": {
            "imports": [
                "portable-net45+wp80+win8+wpa81+dnxcore50"
            ]
        }
    }
}

when I run dotnet run after running dotnet restore --no-cache, I am getting the below error:

$ dotnet run
Can not find runtime target for framework '.NETCoreApp,Version=v1.0' compatible with one of the target runtimes: 'ubuntu.14.04-x64'. Possible causes:
The project has not been restored or restore failed - run dotnet restore
The project does not list one of 'ubuntu.14.04-x64' in the 'runtimes' section.

I added the runtime and did another restore:

{
    "version": "0.0.0",
    "compilationOptions": {
        "emitEntryPoint": true
    },
    "dependencies": {
        "BonVoyage": "*"
    },
    "frameworks": {
        "netcoreapp1.0": {
            "imports": [
                "portable-net45+wp80+win8+wpa81+dnxcore50"
            ]
        }
    },
    "runtimes": {
        "ubuntu.14.04-x64": {}
    }
}

now I am getting this:

$ dotnet run
Project BonVoyage (.NETStandard,Version=v1.1) was previously compiled. Skipping compilation.
Compiling Foo.Sync for .NETCoreApp,Version=v1.0
/home/tugberk/apps/Foo/src/Foo.Sync/project.json(7,25): warning NU1007: Dependency specified was BonVoyage >= * but ended up with BonVoyage 0.0.0-0.

Compilation succeeded.
    1 Warning(s)
    0 Error(s)

Time elapsed 00:00:04.7361717


Could not resolve coreclr path

Not sure about a few things:

• why do I need to specify the runtime inside the project.json file? I expected to do this through the global.json file.
• why am I getting this error?

Environment data

dotnet --info output:

$ dotnet --info
.NET Command Line Tools (1.0.0-rc2-002416)

Product Information:
 Version:     1.0.0-rc2-002416
 Commit Sha:  37f00f24e9

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  14.04
 OS Platform: Linux
 RID:         ubuntu.14.04-x64