Changed Docker detection.

Author: gfraiteur

src/PostSharp.Engineering.BuildTools/Docker/PrologComponent.cs

@@ -30,6 +30,7 @@ public override void WriteDockerfile( StreamWriter writer )
             ENV POWERSHELL_UPDATECHECK=FALSE
             ENV TEMP=C:\Temp
             ENV TMP=C:\Temp
+            ENV RUNNING_IN_DOCKER=TRUE
 
             # Enable long path support
             RUN Set-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem' -Name 'LongPathsEnabled' -Value 1

src/PostSharp.Engineering.BuildTools/Utilities/DockerHelper.cs

@@ -8,7 +8,7 @@ internal static class DockerHelper
 {
     public static bool IsDockerBuild()
     {
-        var s = Environment.GetEnvironmentVariable( "COMPLUS_RUNNING_IN_CONTAINER" );
+        var s = Environment.GetEnvironmentVariable( "RUNNING_IN_DOCKER" );
 
         return s != null && ((bool.TryParse( s, out var b ) && b) || (int.TryParse( s, out var i ) && i != 0));
     }