lto-dump: Do not print output file

lto-dump: Do not print output file

Right now the following is printed:

lto-dump
	.file	"<artificial>"
	.ident	"GCC: (GNU) 13.0.0 20220707 (experimental)"
	.section	.note.GNU-stack,"",@progbits

After the patch we print -help and do not emit any assembly output:

lto-dump
Usage: lto-dump [OPTION]... SUB_COMMAND [OPTION]...

LTO dump tool command line options.

  -list [options]           Dump the symbol list.
    -demangle               Dump the demangled output.
    -defined-only           Dump only the defined symbols.
...

gcc/lto/ChangeLog:

	* lto-dump.cc (lto_main): Exit in the function
	as we don't want any LTO bytecode processing.

gcc/ChangeLog:

	* toplev.cc (init_asm_output): Do not init asm_out_file.