Add workaround for AssemblyInfo and use non-nightly SDK

Ix.NET/Source/Directory.build.targets

@@ -1,5 +1,16 @@
 <Project>
 
+  <!-- Workaround. Remove once we're on 3.1.300+
+  https://github.com/dotnet/sourcelink/issues/572 -->
+  <PropertyGroup>
+    <TargetFrameworkMonikerAssemblyAttributesPath>$([System.IO.Path]::Combine('$(IntermediateOutputPath)','$(TargetFrameworkMoniker).AssemblyAttributes$(DefaultLanguageSourceExtension)'))</TargetFrameworkMonikerAssemblyAttributesPath>
+  </PropertyGroup>
+  <ItemGroup>
+    <EmbeddedFiles Include="$(GeneratedAssemblyInfoFile)"/>
+  </ItemGroup>
+
+
+
   <!-- This props all need to be set in targets as they depend on the values set earlier -->
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard1.0'">
     <DefineConstants>$(DefineConstants);NO_ARRAY_EMPTY;NO_CODE_COVERAGE_ATTRIBUTE</DefineConstants>

Rx.NET/Source/Directory.build.targets

@@ -1,4 +1,15 @@
 <Project>
+
+  <!-- Workaround. Remove once we're on 3.1.300+
+  https://github.com/dotnet/sourcelink/issues/572 -->
+  <PropertyGroup>
+    <TargetFrameworkMonikerAssemblyAttributesPath>$([System.IO.Path]::Combine('$(IntermediateOutputPath)','$(TargetFrameworkMoniker).AssemblyAttributes$(DefaultLanguageSourceExtension)'))</TargetFrameworkMonikerAssemblyAttributesPath>
+  </PropertyGroup>
+  <ItemGroup>
+    <EmbeddedFiles Include="$(GeneratedAssemblyInfoFile)"/>
+  </ItemGroup>
+
+
   <!-- This props all need to be set in targets as they depend on the values set earlier -->
   
   <PropertyGroup>  

Rx.NET/Source/global.json

@@ -1,8 +1,5 @@
 {
   "msbuild-sdks": {
     "MSBuild.Sdk.Extras": "2.0.54"
-  },
-  "sdk": {
-    "version": "3.1.300-preview"
   }
 }

azure-pipelines.ix.yml

@@ -32,11 +32,11 @@ stages:
   jobs:
   - job: Build
     steps:
-    - task: DotNetCoreInstaller@0
+    - task: UseDotNet@2
+      displayName: Use .NET Core 3.1.x SDK
       inputs:
-        version: '3.1.300-preview-015048'
+        version: 3.1.x
         performMultiLevelLookup: true
-        includePreviewVersions: true
 
     - task: DotNetCoreCLI@2
       inputs:

azure-pipelines.rx.yml

@@ -33,11 +33,11 @@ stages:
       DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
 
     steps:
-    - task: DotNetCoreInstaller@0
+    - task: UseDotNet@2
+      displayName: Use .NET Core 3.1.x SDK
       inputs:
-        version: '3.1.300-preview-015048'
+        version: 3.1.x
         performMultiLevelLookup: true
-        includePreviewVersions: true
 
     - task: DotNetCoreCLI@2
       inputs: