Fix verify_type ICE with transparent aggr

[Jan Hubicka]

Hi,
in this testcase we ICE on type variant of TYPE_TRANSPARENT_AGGR type
being !TYPE_TRANSPARENT_AGGR.  

Bootstrapped/regtested x86_64-linux, OK?

        PR c/67581
        * g++.dg/torture/pr67581.C: New testcase.
        * c-family/c-common.c (handle_transparent_union_attribute): Update
        also type variants.

Index: testsuite/g++.dg/torture/pr67581.C
===================================================================
--- testsuite/g++.dg/torture/pr67581.C  (revision 0)
+++ testsuite/g++.dg/torture/pr67581.C  (revision 0)
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+union U 
+{
+  int x; 
+  float y;
+} __attribute__ ((__transparent_union__));
Index: c-family/c-common.c
===================================================================
--- c-family/c-common.c (revision 231020)
+++ c-family/c-common.c (working copy)
@@ -7787,7 +7787,8 @@ handle_transparent_union_attribute (tree
          *node = type = build_duplicate_type (type);
        }
 
-      TYPE_TRANSPARENT_AGGR (type) = 1;
+      for (tree t = TYPE_MAIN_VARIANT (type); t; t = TYPE_NEXT_VARIANT (t))
+        TYPE_TRANSPARENT_AGGR (t) = 1;
       return NULL_TREE;
     }