Add changelog entry about recent llvm change. NFC (#16256)

Author: sbc100

ChangeLog.md

@@ -20,6 +20,9 @@ See docs/process.md for more on how version tagging works.
 
 3.1.4
 -----
+- Due to an llvm change (https://reviews.llvm.org/D118573) some clang flags
+  that did not previously have any effect are now honored (e.g.
+  `-fnew-alignment` and `-fshort-wchar`).
 - llvm dependency updated to 15.0.0 to match upstream. (#16178)
 - The `__EMSCRIPTEN_major__`, `__EMSCRIPTEN_minor__` and `__EMSCRIPTEN_tiny__`
   macros are now available via the `emscripten/version.h` header file.  For the