[LLD] [docs] Mention some notable feature in the release notes

[mstorsjo]

Summary

Trying to fill in releas notes as we go, even though there's a long way to go still until the branch point for 8.0.

LLD can now link clang.exe from object files compiled with GCC 7.x; with GCC 5.x one still needs D52602 though.

[smeenai]

docs/ReleaseNotes.rst

54–55

I'm pretty certain link.exe supports branch islands. They even have optimization options related to that (see /opt:lbr): https://docs.microsoft.com/en-us/cpp/build/reference/opt-optimizations?view=vs-2017

[mstorsjo]

docs/ReleaseNotes.rst

54–55

Oh, ok. I remember testing a pretty synthetic test case which it failed to link though, but maybe it does better with real-word code.

[mstorsjo]

Corrected the statement about link.exe not supporting thunks for arm.

[ruiu]

Maybe you should create a new section, "MinGW Improvements" for mingw improvements? I think most people who uses lld-link don't use lld-link for mingw, and I guess some of them even don't know what it is.

[mstorsjo]

Added a separate section for MinGW related features.

[emaste]

Looks good to me

[ruiu]

LGTM

docs/ReleaseNotes.rst

46

s/lld-link/lld/ for consistency with other notes.

docs/ReleaseNotes.rst

 COFF Improvements
 -----------------
 
 * PDB GUID is set to hash of PDB contents instead to a random byte
   sequence for build reproducibility.
 
 * The following flags have been added: ``/force:multiple``
 
+* In MinGW mode, lld can now automatically import data variables from
+  DLLs without the use of the dllimport attribute.
+
+* lld-link now can link against import libraries produced by GNU tools,
+  and lld with the MinGW frontend can use existing normal MinGW
+  sysroots. ld.lld can handle most object files produced by GCC, and
+  thus works as a drop-in replacement for ld.bfd in such environments.
+
+* lld can create thunks for ARM, to allow linking images over 16 MB
+  (which link.exe doesn't support).
+
 MachO Improvements
 ------------------
 
 * Item 1.