[Bug bootstrap/60830] [4.9 Regression] ICE on bootstrapping on cygwin

["gcc@Denis-Excoffier.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60830

--- Comment #20 from Denis Excoffier <gcc@Denis-Excoffier.org> ---
(In reply to Kai Tietz from comment #12)
> In general it would be of interest
> to learn what destructors (by whom) are present in the list called by
> do_global_dtors (&__DTOR_LIST__)

I've rebuilt everything, under plain cygwin-1.7.29-2, with BOOT_CFLAGS=-g
instead of "-g -O2". I carefully didn't rebuilt anything after the failure in
i686-pc-cygwin/libgcc like before and cc1 seems to work, BUT xgcc still does
not work (with the same symptoms).

xgcc --version (or -dumpspecs) shows something on stdout, but when piped into
wc, there is no output... Strange.

The __DTOR_LIST__ contains a single item: deregister_frame_dtor (see attachment
32602).

Also the specs file is not built (is built empty, see in attachment the
-dumpspecs parameter), this is probably the cause of the "xgcc: error:
unrecognized command line option 'X'" (with X=--version, or -mtune=generic, or
-march=pentiumpro) when the -B/tmp/lcl/tmp/gcc/obj/gcc/ option is used.