Also check e_machine when merging sections

Also check e_machine when merging sections

When we check consistency for merge ELF sections, we should not only
check EI_CLASS, but also compatible e_machine.

bfd/

	PR ld/19013
	* elflink.c (_bfd_elf_merge_sections): Only merge input bfds
	that have the compatible ELF machine code with the output bfd.

ld/testsuite/

	PR ld/19013
	* ld-x86-64/pr19013-nacl.d: New file.
	* ld-x86-64/pr19013-x32.d: Likewise.
	* ld-x86-64/pr19013.d: Likewise.
	* ld-x86-64/pr19013.s: Likewise.
	* ld-x86-64/x86-64.exp: Run PR ld/19013 tests.