[Bug target/67172] [5/6 regression] i686-w64-mingw32 dwarf2 bootstrap fails with undefined reference to __EH_FRAME_BEGIN__

[breedlove.matt at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67172

--- Comment #1 from Matt Breedlove <breedlove.matt at gmail dot com> ---
Seems to have started with r214954.  Here's the direct link to the ML post:

https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00409.html

Per discussions with Kai, EH_FRAME_SECTION_NAME shouldn't be getting defined
for mingw-w64 which it isn't while compiling libgcc2.c however the change to
using _LIBGCC_EH_FRAME_SECTION_NAME__ which *is* defined while compiling this
file ends up breaking linking.  This is mingw specific as the modified code is
in a block surrounded by an #ifndef __CYGWIN__.  The complexities of gcc's
dwarf2 code especially during bootstrapping are a bit beyond me.  The patch
above merely restores GCC 4.9 behavior for mingw but whether the change should
be implemented there or in a target-specific section, I'm not sure.