Windows: keep using Windows PowerShell, other OSs fall back on pwsh (to reduce deps to get up and running on Windows)

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -624,7 +624,10 @@
   </ItemGroup>
 
   <Target Name="ILSpyUpdateAssemblyInfo" BeforeTargets="BeforeBuild">
-    <PropertyGroup>
+    <PropertyGroup Condition=" '$(OS)' == 'Windows_NT' ">
+      <UpdateAssemblyInfo>powershell -NoProfile -ExecutionPolicy Bypass -File BuildTools/update-assemblyinfo.ps1 $(Configuration)</UpdateAssemblyInfo>
+    </PropertyGroup>
+    <PropertyGroup Condition=" '$(OS)' != 'Windows_NT' ">
       <UpdateAssemblyInfo>pwsh -NoProfile -ExecutionPolicy Bypass -File BuildTools/update-assemblyinfo.ps1 $(Configuration)</UpdateAssemblyInfo>
     </PropertyGroup>
     <Exec WorkingDirectory=".." Command="$(UpdateAssemblyInfo)" Timeout="60000" />

README.md

@@ -45,7 +45,6 @@ Windows:
   - Workload "Visual Studio extension development" (ILSpy.sln contains a VS extension project)
   - Individual Component "MSVC v142 - VS 2019 C++ x64/x86 build tools (v14.23)" (or similar)
     - The VC++ toolset is optional; if present it is used for `editbin.exe` to modify the stack size used by ILSpy.exe from 1MB to 16MB, because the decompiler makes heavy use of recursion, where small stack sizes lead to problems in very complex methods.
-- Make sure [PowerShell](https://github.com/PowerShell/PowerShell) is installed (formerly known as PowerShell Core) - recommended way of installation via [choco install powershell-core](https://chocolatey.org/packages/powershell-core)
 - Check out the ILSpy repository using git.
 - Execute `git submodule update --init --recursive` to download the ILSpy-Tests submodule (used by some test cases).
 - Open ILSpy.sln in Visual Studio.