dotnet20 build fixes (#365)

Fix the dotnet20 build, use docker for builds, and re-enable dotnet20 in the release script.

environments/dotnet20/README.md

@@ -63,7 +63,7 @@ Move to the build directory inside the container and restore the packages:
 
 ```
 cd /build 
-dotnet restore
+dotnet restore fission-dotnet20.csproj
 log  : Restoring packages for /source/project.json...
 log  : Installing System.Net.WebSockets 4.0.0.
 log  : Installing runtime.native.System.IO.Compression 4.1.0.

environments/dotnet20/build.sh

@@ -1,4 +1,6 @@
 #!/bin/sh
-dotnet restore
-dotnet publish -c Release -o out
-docker build -t fission/dotnet20-env .
+
+THIS_DIR=$(realpath $(dirname $0))
+
+docker run -v $THIS_DIR:/proj microsoft/dotnet:2.0.0-sdk sh -c "cd /proj && ./project-build.sh"
+

environments/dotnet20/project-build.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+dotnet restore fission-dotnet20.csproj
+dotnet publish fission-dotnet20.csproj -c Release -o out

hack/release.sh

@@ -118,7 +118,7 @@ build_and_push_all_envs() {
     build_and_push_env_image $version nodejs node-env
     build_and_push_env_image $version binary binary-env
     build_and_push_env_image $version dotnet dotnet-env
-    # (See #359) build_and_push_env_image $version dotnet20 dotnet20-env
+    build_and_push_env_image $version dotnet20 dotnet20-env
     build_and_push_env_image $version go go-env
     build_and_push_env_image $version perl perl-env
     build_and_push_env_image $version php7 php-env