Use checked-in key to build ReleaseSigned

csharp/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj

@@ -55,7 +55,7 @@
     <GenerateSerializationAssemblies>Off</GenerateSerializationAssemblies>
     <Prefer32Bit>false</Prefer32Bit>
     <SignAssembly>True</SignAssembly>
-    <AssemblyOriginatorKeyFile>C:\keys\Google.Protobuf.snk</AssemblyOriginatorKeyFile>
+    <AssemblyOriginatorKeyFile>..\..\keys\Google.Protobuf.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="mscorlib" />

csharp/src/Google.Protobuf/Google.Protobuf.csproj

@@ -64,7 +64,7 @@
     <NoStdLib>true</NoStdLib>
     <GenerateSerializationAssemblies>Off</GenerateSerializationAssemblies>
     <SignAssembly>True</SignAssembly>
-    <AssemblyOriginatorKeyFile>C:\keys\Google.Protobuf.snk</AssemblyOriginatorKeyFile>
+    <AssemblyOriginatorKeyFile>..\..\keys\Google.Protobuf.snk</AssemblyOriginatorKeyFile>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>