Revert "sayonara appveyor"

This reverts commit 3b9cfc7c50.

Common.props

@@ -1,7 +1,7 @@
 <Project>
 	<PropertyGroup>
 		<AnalysisLevel>5</AnalysisLevel>
-		<ContinuousIntegrationBuild Condition=" '$(GITLAB_CI)' != '' ">true</ContinuousIntegrationBuild>
+		<ContinuousIntegrationBuild Condition=" '$(GITLAB_CI)' != '' Or '$(APPVEYOR)' != '' ">true</ContinuousIntegrationBuild>
 		<EnableNETAnalyzers>true</EnableNETAnalyzers>
 		<ErrorReport>prompt</ErrorReport>
 		<IsTargetingNetFramework>$(TargetFramework.StartsWith("net4"))</IsTargetingNetFramework>

appveyor.yml

@@ -0,0 +1,36 @@
+version: 0.0.0.{build}
+branches:
+  only:
+  - master
+image: Visual Studio 2022
+assembly_info:
+  patch: true
+  file: '**\AssemblyInfo.*'
+  assembly_version: '{version}'
+  assembly_file_version: '{version}'
+  assembly_informational_version: '{version}'
+build_script:
+- cmd: >-
+    SET TS=%APPVEYOR_REPO_COMMIT_TIMESTAMP%
+
+    SET BUILDCODE=%TS:~0,10%-%TS:~11,2%%TS:~14,2%%TS:~17,2%-#%APPVEYOR_REPO_COMMIT%
+
+    SET BUILDFILE=BizHawk_Developer-%BUILDCODE%.zip
+
+    echo %BUILDFILE%
+
+
+    cd dist
+
+    call QuickTestBuildAndPackage_Developer.bat
+
+
+    move BizHawk-Developer.zip ..\%BUILDFILE%
+
+
+    cd ..
+
+    appveyor PushArtifact %BUILDFILE%
+
+
+    rem appveyor UpdateBuild -Version %BUILDFILE%

src/BizHawk.Tests/BizHawk.Tests.csproj

@@ -2,6 +2,9 @@
 	<PropertyGroup>
 		<TargetFramework>net6.0</TargetFramework>
 	</PropertyGroup>
+	<PropertyGroup Condition=" '$(APPVEYOR)' != '' ">
+		<TargetFramework>netcoreapp3.1</TargetFramework>
+	</PropertyGroup>
 	<Import Project="../MainSlnCommon.props" />
 	<PropertyGroup>
 		<DefineConstants Condition=" '$(ContinuousIntegrationBuild)' == 'true' ">$(DefineConstants);SKIP_PLATFORM_TESTS</DefineConstants>