Pass const frame_info_ptr reference for skip_[language_]trampoline

Pass const frame_info_ptr reference for skip_[language_]trampoline

g++ 13.1.1 produces a -Werror=dangling-pointer=

In file included from ../../binutils-gdb/gdb/frame.h:75,
                 from ../../binutils-gdb/gdb/symtab.h:40,
                 from ../../binutils-gdb/gdb/language.c:33:
In member function ‘void intrusive_list<T, AsNode>::push_empty(T&) [with T = frame_info_ptr; AsNode = intrusive_base_node<frame_info_ptr>]’,
    inlined from ‘void intrusive_list<T, AsNode>::push_back(reference) [with T = frame_info_ptr; AsNode = intrusive_base_node<frame_info_ptr>]’ at gdbsupport/intrusive_list.h:332:24,
    inlined from ‘frame_info_ptr::frame_info_ptr(const frame_info_ptr&)’ at gdb/frame.h:241:26,
    inlined from ‘CORE_ADDR skip_language_trampoline(frame_info_ptr, CORE_ADDR)’ at gdb/language.c:530:49:
gdbsupport/intrusive_list.h:415:12: error: storing the address of local variable ‘<anonymous>’ in ‘frame_info_ptr::frame_list.intrusive_list<frame_info_ptr>::m_back’ [-Werror=dangling-pointer=]
  415 |     m_back = &elem;
      |     ~~~~~~~^~~~~~~
gdb/language.c: In function ‘CORE_ADDR skip_language_trampoline(frame_info_ptr, CORE_ADDR)’:
gdb/language.c:530:49: note: ‘<anonymous>’ declared here
  530 |       CORE_ADDR real_pc = lang->skip_trampoline (frame, pc);
      |                           ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
gdb/frame.h:359:41: note: ‘frame_info_ptr::frame_list’ declared here
  359 |   static intrusive_list<frame_info_ptr> frame_list;
      |                                         ^~~~~~~~~~

Each new frame_info_ptr is being pushed on a static frame list and g++
cannot see why that is safe in case the frame_info_ptr is created and
destroyed immediately when passed as value.

It isn't clear why only in this one place g++ sees the issue (probably
because it can inline enough code in this specific case).

Since passing the frame_info_ptr as const reference is cheaper, use
that as workaround for this warning.

PR build/30413
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30413

Tested-by: Kevin Buettner <kevinb@redhat.com>
Reviewed-by: Kevin Buettner <kevinb@redhat.com>
Reviewed-by: Tom Tromey <tom@tromey.com>