make gcc-uno bridge work with both gcc-4.7 and clang

It seems b0515ea5 and e2b7e28c
conflict, clang requires the extra call, gcc-4.7 crashes with it.

bridges/source/cpp_uno/gcc3_linux_intel/callvirtualmethod.cxx

@@ -67,7 +67,9 @@ void CPPU_CURRENT_NAMESPACE::callVirtualMethod(
         // unexpected size of int
     assert(nStackLongs && pStackLongs); // no stack
 
+#ifdef __clang__
     if (! pAdjustedThisPtr) CPPU_CURRENT_NAMESPACE::dummy_can_throw_anything("xxx"); // address something
+#endif
 
     volatile long edx = 0, eax = 0; // for register returns
     void * stackptr;