re PR debug/40521 (-g causes GCC to generate .eh_frame)

	PR debug/40521
	* debug.h (struct gcc_debug_hooks): Add assembly_start hook.
	* cgraphunit.c (cgraph_optimize): Call it.
	* dwarf2out.c (dwarf2out_init): Move .cfi_sections printing into...
	(dwarf2out_assembly_start): ... here.  New hook.
	(dwarf2out_debug_hooks): Add dwarf2out_assembly_start.
	* debug.c (do_nothing_debug_hooks): Do nothing for assembly_start
	hook.
	* dbxout.c (dbx_debug_hooks, xcoff_debug_hooks): Likewise.
	* sdbout.c (sdb_debug_hooks): Likewise.
	* vmsdbgout.c (vmsdbg_debug_hooks): Add vmsdbgout_assembly_start.
	(vmsdbgout_assembly_start): New hook.

From-SVN: r152930