Merge pull request #1502 from b0urb4k1/master

Make ExitCode variable

src/app/FakeLib/TargetHelper.fs

@@ -474,7 +474,8 @@ let WriteTaskTimeSummary total =
 
 module ExitCode =
     let exitCode = ref 0
-let private changeExitCodeIfErrorOccured() = if errors <> [] then Environment.ExitCode <- 42; ExitCode.exitCode := 42
+    let mutable Value = 42
+let private changeExitCodeIfErrorOccured() = if errors <> [] then Environment.ExitCode <- ExitCode.Value; ExitCode.exitCode := ExitCode.Value
 
 /// [omit]
 let isListMode = hasBuildParam "list"