Update nuget and sln

Summary:
Update nuget CI
Closes https://github.com/facebook/yoga/pull/463

Reviewed By: emilsjolander

Differential Revision: D4666500

Pulled By: splhack

fbshipit-source-id: 1d77457d59eafe6de855a27b4f8a8567cd415b7b

csharp/build-native.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+echo $ANDROID_SDK
 if buck --version >/dev/null 2>&1; then true; else
     echo "Building Buck!"
     mkdir lib