Working around compilation error with NVC.

Author: LarsAsplund

vunit/vhdl/data_types/test/tb_codec.vhd

@@ -40,12 +40,14 @@ begin
     function "=" (
       constant l, r : ieee.numeric_bit.unsigned)
       return boolean is
+      variable result : boolean;
     begin
       if l'length = 0 and r'length = 0 then
         return true;
       end if;
 
-      return ieee.numeric_bit."="(l, r);
+      result := ieee.numeric_bit."="(l, r);
+      return result;
     end function "=";
 
     function "=" (