Add bazel rule to build C# release artifacts

csharp/BUILD.bazel

@@ -51,3 +51,9 @@ pkg_files(
     strip_prefix = strip_prefix.from_root(""),
     visibility = ["//pkg:__pkg__"],
 )
+
+sh_binary(
+  name = "csharp_release_build",
+  srcs = ["csharp_release_build.sh"],
+  args = ["$(location csharp_release_build.sh)"],
+)

csharp/csharp_release_build.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+cd $(dirname $(readlink $BASH_SOURCE))
+
+#Disable some unwanted dotnet options
+set DOTNET_SKIP_FIRST_TIME_EXPERIENCE=true
+set DOTNET_CLI_TELEMETRY_OPTOUT=true
+
+#Work around https://github.com/dotnet/core/issues/5881
+dotnet nuget locals all --clear
+
+#Builds Google.Protobuf NuGet packages
+dotnet restore src/Google.Protobuf.sln
+dotnet pack -c Release src/Google.Protobuf.sln -p:ContinuousIntegrationBuild=true
+
+#This requires built protoc executables as specified in the nusepc
+nuget pack Google.Protobuf.Tools.nuspec