Minor tweaks to make KoreBuild 2.0 run on Linux

src/Microsoft.AspNetCore.Build/scripts/KoreBuild.sh

@@ -77,7 +77,7 @@ ensure_dotnet() {
     versionFile="$DOTNET_VERSION_DIR/cli.version"
     version=$(<$versionFile)
 
-    [ -z "$KOREBUILD_DOTNET_CHANNEL" ] && KOREBUILD_DOTNET_CHANNEL=rel-1.0.0
+    [ -z "$KOREBUILD_DOTNET_CHANNEL" ] && KOREBUILD_DOTNET_CHANNEL=preview
     [ -z "$KOREBUILD_DOTNET_VERSION" ] && KOREBUILD_DOTNET_VERSION=$version
 
     if [ ! -z "$KOREBUILD_SKIP_RUNTIME_INSTALL" ]; then

src/Microsoft.AspNetCore.Build/scripts/msbuild.project.template.json

@@ -8,6 +8,7 @@
         "NETStandard.Library": "1.6.0",
         "Microsoft.NETCore.TestHost": "1.0.0",
         "Microsoft.NETCore.Runtime.CoreCLR": "1.0.3",
+        "Microsoft.NETCore.Platforms": "1.1.0-*",
         "System.Dynamic.Runtime": "4.0.11",
         "NuGet.CommandLine.Xplat": "3.5.0-beta-final",
         "Microsoft.Build.Runtime": "15.1.0-preview-000370-00"