fix #14873 properly by skipping abi field in importc type (#17944)

* fix #14873 properly by skipping `abi` field in importc type

* add test

* fix test for windows

tests/stdlib/uselocks.nim

@@ -11,5 +11,21 @@ proc use* (m: var MyType): int =
     result = 3
 
 block:
+  # bug #14873
   var l: Lock
-  doAssert $l == "()"
+  doAssert ($l).len > 0
+    # on posix, "()", on windows, something else, but that shouldn't be part of the spec
+    # what matters is that `$` doesn't cause the codegen bug mentioned
+
+when true: # intentional
+  # bug https://github.com/nim-lang/Nim/issues/14873#issuecomment-784241605
+  type
+    Test = object
+      path: string # Removing this makes both cases work.
+      lock: Lock
+  # A: This is not fine.
+  var a = Test()
+  proc main(): void =
+    # B: This is fine.
+    var b = Test()
+  main()