Update changelog for LLVM fixes in r27b.

Bug: android/ndk#2040
Bug: android/ndk#2054
Bug: android/ndk#2059
Test: None
(cherry picked from https://android-review.googlesource.com/q/commit:18c7da11a92d0538c0c351d5eda0b0303cffe1c7)
Merged-In: Iaceabc1a94460e879e063a833af03a9c094d2286
Change-Id: Iaceabc1a94460e879e063a833af03a9c094d2286

docs/changelogs/Changelog-r27.md

@@ -29,6 +29,11 @@ directly, see the [build system maintainers guide].
 
 ## r27b
 
+* Updated LLVM to clang-r522817b. See `clang_source_info.md` in the toolchain
+  directory for version information.
+  * [Issue 2040]: Fixed miscompile with indirect gotos.
+  * [Issue 2054]: Fixed crash in x86 fp16 instruction selection.
+  * [Issue 2059]: Fixed infinite loop in aarch64 vector instruction selection.
 * [Issue 2032]: Fixed compatibility issues with projects that used a very old
   `cmake_minimum_required` version ("Policy CMP0057 is not set: Support new
   IN_LIST if() operator").
@@ -42,7 +47,10 @@ directly, see the [build system maintainers guide].
 
 [Issue 2032]: https://github.com/android/ndk/issues/2032
 [Issue 2039]: https://github.com/android/ndk/issues/2039
+[Issue 2040]: https://github.com/android/ndk/issues/2040
 [Issue 2049]: https://github.com/android/ndk/issues/2049
+[Issue 2054]: https://github.com/android/ndk/issues/2054
+[Issue 2059]: https://github.com/android/ndk/issues/2059
 [CMake's docs]: https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html#cross-compiling-for-android-with-the-ndk
 [toolchain file]: https://developer.android.com/ndk/guides/cmake