Fix PowerShell PostBuild failing when solution path contains spaces

Quote the $(ProjectDir) and $(TargetDir) MSBuild properties in the
Copy-Item commands so that paths with spaces are handled correctly.

ICSharpCode.Decompiler.PowerShell/ICSharpCode.Decompiler.PowerShell.csproj

@@ -24,7 +24,7 @@
   </ItemGroup>
 
   <Target Name="PostBuild" AfterTargets="PostBuildEvent">
-    <Exec Condition=" '$(OS)' == 'Windows_NT' " Command="powershell -Command &quot;Copy-Item $(ProjectDir)manifest.psd1 $(TargetDir)$(TargetName).psd1&quot;" />
-	<Exec Condition=" '$(OS)' != 'Windows_NT' " Command="pwsh -Command &quot;Copy-Item $(ProjectDir)manifest.psd1 $(TargetDir)$(TargetName).psd1&quot;" />
+    <Exec Condition=" '$(OS)' == 'Windows_NT' " Command="powershell -Command &quot;Copy-Item '$(ProjectDir)manifest.psd1' '$(TargetDir)$(TargetName).psd1'&quot;" />
+	<Exec Condition=" '$(OS)' != 'Windows_NT' " Command="pwsh -Command &quot;Copy-Item '$(ProjectDir)manifest.psd1' '$(TargetDir)$(TargetName).psd1'&quot;" />
   </Target>
 </Project>