Validate -pie if PIE is enabled by default

When PIE is enabled by default, -pie is treated as nop in driver.  We
should simply validate it, instead of issue an error.

	* gcc.c (driver_handle_option): Validate -pie if PIE is enabled
	by default.

From-SVN: r224987

gcc/ChangeLog

+2015-06-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* gcc.c (driver_handle_option): Validate -pie if PIE is enabled
+	by default.
+
 2015-06-25  Andrew MacLeod  <amacleod@redhat.com>
 
 	* function.h (ipa_opt_pass, ipa_opt_pass_d): Move forward declarations.

gcc/gcc.c

@@ -3893,6 +3893,11 @@ driver_handle_option (struct gcc_options *opts,
       save_switch ("-o", 1, &arg, validated, true);
       return true;
 
+#ifdef ENABLE_DEFAULT_PIE
+    case OPT_pie:
+      /* -pie is turned on by default.  */
+#endif
+
     case OPT_static_libgcc:
     case OPT_shared_libgcc:
     case OPT_static_libgfortran: