detect OpenBSD

Index: src/gui/qmlUtils.nim
--- src/gui/qmlUtils.nim.orig
+++ src/gui/qmlUtils.nim
@@ -69,7 +69,7 @@ qobject FileDialogs:
   proc showInExplorer(path: string) =
     let file = if path.startsWith("file:"): path[5..^1] else: path
     
-    when defined(linux):
+    when defined(linux) or defined(openbsd):
       # try to open dolphin
       if execShellCmd("dolphin --select " & file.quoted) == 0: return
 
