* common.opt: Add -gdwarf.
	* opts.c (common_handle_option): Handle it.
	* gcc.c (ASM_DEBUG_SPEC): Don't expect "-2" for DWARF.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@197675 138bc75d-0d04-0410-961f-82ee72b054a4

Conflicts:
	gcc/ChangeLog