Also validate $? for $lastexitcode

Resolves #52

Author: JanDeDobbeleer

oh-my-posh.psm1

@@ -12,7 +12,7 @@ function Set-Prompt {
     Import-Module $sl.CurrentThemeLocation -Force
 
     [ScriptBlock]$Prompt = {
-        $lastCommandFailed = $global:error.Count -gt $sl.ErrorCount
+        $lastCommandFailed = ($global:error.Count -gt $sl.ErrorCount) -or -not $?
         $sl.ErrorCount = $global:error.Count
 
         #Start the vanilla posh-git when in a vanilla window, else: go nuts