[LLD] [docs] Add a known limitation to the comment about lld supporting GCC/MinGW object files. NFC.

[mstorsjo]

Summary

It's a rather long-winded comment, but we still want to announce that we mostly work out of the box with existing sysroots, just not ones with dwarf exceptions.

For libunwind with dwarf exceptions, a GCC style crtend.o with a terminator isn't needed, so it doesn't matter in such setups. For existing GCC setups, i686 either uses dwarf or SjLj (both are pretty much equally common I think), while the x86_64 ones either use SEH or SjLj.

[ruiu]

LGTM

docs/ReleaseNotes.rst

63–64

dwarf -> DWARF

docs/ReleaseNotes.rst

 ------------------
 
 * lld can now automatically import data variables from DLLs without the
   use of the dllimport attribute.
 
 * lld can now use existing normal MinGW sysroots with import libraries and
   CRT startup object files for GNU binutils. lld can handle most object
   files produced by GCC, and thus works as a drop-in replacement for
-  ld.bfd in such environments.
+  ld.bfd in such environments. (There are known issues with linking crtend.o
+  from GCC in setups with dwarf exceptions though, where object files are
+  linked in a different order than with GNU ld, inserting a dwarf exception
+  table terminator too early.)
 
 MachO Improvements
 ------------------
 
 * Item 1.
 
 WebAssembly Improvements
 ------------------------
 
 * Add initial support for creating shared libraries (-shared).
   Note: The shared library format is still under active development and may
   undergo significant changes in future versions.
   See: https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md