perform a fixpoint iteration for proper Nimscript support

src/nimble.nim

@@ -1021,7 +1021,10 @@ proc doAction(options: Options) =
   # re-read it from the compiler.
   # TODO: It doesn't appear that this actually happens, can we just remove this?
   var command = compiler_options.command.parseActionType()
-
+  var doLoop = true
+  while doLoop:
+    doLoop = false
+    let cmd = compiler_options.command.normalize
     case command
     of actionUpdate:
       update(options)
@@ -1047,8 +1050,11 @@ proc doAction(options: Options) =
       publish(pkgInfo)
     of actionDump:
       dump(options)
-  of actionNil, actionCustom:
-    assert false
+    of actionNil: discard "assuming nimscript 'nop' command here"
+    of actionCustom:
+      # calls Nimscript as a side effect :-/
+      discard getPkgInfo(getCurrentDir())
+      doLoop = cmd != compiler_options.command.normalize
 
 when isMainModule:
   when defined(release):