Add multiple safeties around the RemoveDir task

So that we don't end up nuking the whole git repository!

It was my misunderstanding that targets setup with `AfterTargets` would not run if the target specified was skipped because its condition would evaluate to false. When trying to add multitargeting, the `MoveCoverletReport` target ran anyway and the `CoverletReport` item evaluated to empty which in turn made `CoverletReportParentDirectory` evaluate to `..`, i.e the root of the git repository which was then deleted by the `RemoveDir` task.

Two safeties have been added:
1. Add the same `Condition="$(TargetFramework) != ''"` on all targets running after `GenerateHtmlCoverageReport`.
1. Add `Condition="$(CoverletReport) != ''"` when defining the `CoverletReportParentDirectory` item.

This incident would never have happened in the first place if:
1. I could have used `$([System.IO.Directory]::GetParent($(CoverletReport)))` instead of `$([System.IO.Path]::Combine($(CoverletReport),'..'))` because the former would have crashed when `$(CoverletReport)` evaluates to empty, the latter just silently picked the wrong parent directory. But I did not use the former because of a [Rider bug][1].
2. VS Test would not [create test results in non deterministic paths][2]. The `MoveCoverletReport` target would not have been needed at all.

[1]: https://youtrack.jetbrains.com/issue/RIDER-92994
[2]: microsoft/vstest#2378

Author: 0xced

tests/Serilog.Formatting.Log4Net.Tests.csproj

@@ -44,26 +44,26 @@
   </Target>
 
   <!-- Because of https://github.com/microsoft/vstest/issues/2378 -->
-  <Target Name="MoveCoverletReport" AfterTargets="GenerateHtmlCoverageReport">
+  <Target Name="MoveCoverletReport" AfterTargets="GenerateHtmlCoverageReport" Condition="$(TargetFramework) != ''">
     <Move SourceFiles="@(CoverletReport)" DestinationFolder="$(CoverageReportDirectory)" />
     <PropertyGroup>
       <CoverletReport>@(CoverletReport)</CoverletReport>
     </PropertyGroup>
     <ItemGroup>
-      <CoverletReportParentDirectory Include="$([System.IO.Path]::Combine($(CoverletReport),'..'))" />
+      <CoverletReportParentDirectory Include="$([System.IO.Path]::Combine($(CoverletReport),'..'))" Condition="$(CoverletReport) != ''" />
     </ItemGroup>
     <RemoveDir Directories="@(CoverletReportParentDirectory)" />
   </Target>
 
-  <Target Name="DisplayCoverageSummary" AfterTargets="MoveCoverletReport">
+  <Target Name="DisplayCoverageSummary" AfterTargets="MoveCoverletReport" Condition="$(TargetFramework) != ''">
     <PropertyGroup>
       <CatCommand Condition="!$([MSBuild]::IsOSPlatform('Windows'))">cat</CatCommand>
       <CatCommand Condition="$([MSBuild]::IsOSPlatform('Windows'))">type</CatCommand>
     </PropertyGroup>
     <Exec WorkingDirectory="$(CoverageReportDirectory)" Command="$(CatCommand) Summary.txt" />
   </Target>
 
-  <Target Name="OpenHtmlCoverageReport" AfterTargets="MoveCoverletReport" Condition="$(ContinuousIntegrationBuild) != 'true'">
+  <Target Name="OpenHtmlCoverageReport" AfterTargets="MoveCoverletReport" Condition="$(TargetFramework) != '' AND $(ContinuousIntegrationBuild) != 'true'">
     <PropertyGroup>
       <OpenCommand Condition="$([MSBuild]::IsOSPlatform('Linux'))">xdg-open</OpenCommand>
       <OpenCommand Condition="$([MSBuild]::IsOSPlatform('OSX'))">open</OpenCommand>