x86-64: Correct unwind info for the BND PLT

x86-64: Correct unwind info for the BND PLT

Since the BND PLT has

 230:	68 00 00 00 00       	pushq  $0x0
 235:	f2 e9 e5 ff ff ff    	bnd jmpq 220 <.plt>
 23b:	0f 1f 44 00 00       	nopl   0x0(%rax,%rax,1)

instead of

 230:	ff 25 e2 0d 20 00    	jmpq   *0x200de2(%rip)        # 201018
<func>
 236:	68 00 00 00 00       	pushq  $0x0
 23b:	e9 e0 ff ff ff       	jmpq   220 <.plt>

its unwind info should be

DW_CFA_def_cfa_expression (DW_OP_breg7 (rsp): 8; DW_OP_breg16 (rip): 0;
DW_OP_lit15; DW_OP_and; DW_OP_lit5; DW_OP_ge; DW_OP_lit3; DW_OP_shl;
DW_OP_plus)

bfd/

	PR ld/21038
	* elf64-x86-64.c (elf_x86_64_eh_frame_bnd_plt): New.
	(elf_x86_64_bnd_arch_bed): Use elf_x86_64_eh_frame_bnd_plt and
	elf_x86_64_eh_frame_plt_got.
	(elf_x86_64_size_dynamic_sections): Get unwind info from
	elf_x86_64_bnd_arch_bed for the BND PLT.

ld/

	PR ld/21038
	* testsuite/ld-x86-64/pr21038a.d: New file.
	* testsuite/ld-x86-64/pr21038a.s: Likewise.
	* testsuite/ld-x86-64/pr21038b.d: Likewise.
	* testsuite/ld-x86-64/pr21038b.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run pr21038a and pr21038b.