Make sure that update-assemblyinfo.ps1 fails if PowerShell >= 5.0 is not installed.

BuildTools/update-assemblyinfo.ps1

@@ -1,4 +1,9 @@
-$ErrorActionPreference = "Stop"
+if (-not ($PSVersionTable.PSCompatibleVersions -contains "5.0")) {
+    Write-Error "This script requires at least powershell version 5.0!";
+    return 255;
+}
+
+$ErrorActionPreference = "Stop"
 
 $baseCommit = "d779383cb85003d6dabeb976f0845631e07bf463";
 $baseCommitRev = 1;
@@ -98,7 +103,7 @@ try {
     }
 
     if (-not (Test-File "ILSpy.sln")) {
-        Write-Host "Working directory must be the ILSpy repo root!";
+        Write-Error "Working directory must be the ILSpy repo root!";
         return 2;
     }
 

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -685,7 +685,7 @@
     <Exec ContinueOnError="true" WorkingDirectory=".." Command="$(GitRevParse)" ConsoleToMSBuild="true">
       <Output TaskParameter="ConsoleOutput" PropertyName="CommitHash" />
     </Exec>
-    <Exec WorkingDirectory=".." Command="$(UpdateAssemblyInfo)" Timeout="60000" Condition="'$(CommitHash)'!='$(LastCommitHash)'" />
+    <Exec WorkingDirectory=".." Command="$(UpdateAssemblyInfo)" Timeout="60000" Condition="'$(CommitHash)'!='$(LastCommitHash)'" LogStandardErrorAsError="true" ContinueOnError="false" />
     <WriteLinesToFile Lines="$(CommitHash)" File="@(UpdateAssemblyInfoStamp)" Overwrite="true" Condition="'$(CommitHash)'!='$(LastCommitHash)'" />
     <ReadLinesFromFile ContinueOnError="true" File="..\VERSION">
       <Output TaskParameter="Lines" PropertyName="PackageVersion" />

README.md

@@ -45,6 +45,7 @@ How to build
 
 #### Windows:
 
+- Make sure PowerShell (at least version) 5.0 is installed.
 - Clone the ILSpy repository using git.
 - Execute `git submodule update --init --recursive` to download the ILSpy-Tests submodule (used by some test cases).
 - Install Visual Studio (documented version: 17.1). You can install the necessary components in one of 3 ways: