[GOLD, PowerPC] Add --no-stub-group-multi

The trouble with stubs per output section is that ppc32 uses a plt
stub as the address of a global function.  This needs to be unique,
otherwise we'll get multiple addresses for a function.

Obviously this is only a partial solution, since ppc32 will get
multiple stubs when code is larger than 33M.  A proper fix will
involve selecting a unique stub to use for non-branch relocs.

	* options.h (stub-group-multi): Default to true.  Add
	--no-stub-group-multi.

Author: amodra

gold/ChangeLog

@@ -1,3 +1,8 @@
+2017-09-19  Alan Modra  <amodra@gmail.com>
+
+	* options.h (stub-group-multi): Default to true.  Add
+	--no-stub-group-multi.
+
 2017-08-30  Alan Modra  <amodra@gmail.com>
 
 	* powerpc.cc (Target_powerpc::Relocate::relocate): Nop addis on

gold/options.h

@@ -1235,9 +1235,10 @@ class General_options
 		"stubs are always after the group. 1 means use default size"),
 	     N_("SIZE"));
 
-  DEFINE_bool(stub_group_multi, options::TWO_DASHES, '\0', false,
+  DEFINE_bool(stub_group_multi, options::TWO_DASHES, '\0', true,
 	      N_("(PowerPC only) Allow a group of stubs to serve multiple "
-		 "output sections"), NULL);
+		 "output sections"),
+	      N_("(PowerPC only) Each output section has its own stubs"));
 
   DEFINE_uint(split_stack_adjust_size, options::TWO_DASHES, '\0', 0x4000,
 	      N_("Stack size when -fsplit-stack function calls non-split"),