Update ChangeLog and readme.txt

Author: aheejin

ChangeLog.md

@@ -20,6 +20,7 @@ See docs/process.md for more on how version tagging works.
 
 3.1.73 (in development)
 -----------------------
+- compiler-rt was updated to LLVM 19.1.4. (#22937)
 
 3.1.72 - 11/19/24
 -----------------

system/lib/compiler-rt/readme.txt

@@ -1,14 +1,14 @@
 llvm's compiler-rt
 ------------------
 
-These files are from the llvm-project based on release 17.0.4.
+These files are from the llvm-project based on release 19.1.4.
 
 We maintain a local fork of llvm-project that contains any emscripten
 specific patches:
 
   https://github.com/emscripten-core/llvm-project
 
-The current patch is based on the emscripten-libs-17 branch.
+The current patch is based on the emscripten-libs-19 branch.
 
 Update Instructions
 -------------------
@@ -20,4 +20,4 @@ Modifications
 
 For a list of changes from upstream see the compiler-rt files that are part of:
 
-https://github.com/llvm/llvm-project/compare/llvmorg-17.0.4...emscripten-core:emscripten-libs-17
+https://github.com/llvm/llvm-project/compare/llvmorg-19.1.4...emscripten-core:emscripten-libs-19