Bump to LLVM 19 on 3.13

Author: zanieb

cpython-unix/build-cpython.sh

@@ -428,6 +428,12 @@ if [ -n "${CPYTHON_OPTIMIZED}" ]; then
     # Allow users to enable the experimental JIT on 3.13+
     if [[ -n "${PYTHON_MEETS_MINIMUM_VERSION_3_13}" ]]; then
         CONFIGURE_FLAGS="${CONFIGURE_FLAGS} --enable-experimental-jit=yes-off"
+
+        if [[ -n "${PYTHON_MEETS_MAXIMUM_VERSION_3_13}" ]]; then
+            # On 3.13, LLVM 18 is hard-coded into the configure script. Override it to our toolchain
+            # version.
+            patch -p1 -i "${ROOT}/patch-jit-llvm-19.patch"
+        fi
     fi
 fi
 

cpython-unix/patch-jit-llvm-19.patch

@@ -0,0 +1,12 @@
+diff --git a/Tools/jit/_llvm.py b/Tools/jit/_llvm.py
+--- a/Tools/jit/_llvm.py
++++ b/Tools/jit/_llvm.py
+@@ -8,7 +8,7 @@
+ import subprocess
+ import typing
+ 
+-_LLVM_VERSION = 18
++_LLVM_VERSION = 19
+ _LLVM_VERSION_PATTERN = re.compile(rf"version\s+{_LLVM_VERSION}\.\d+\.\d+\S*\s+")
+ 
+ _P = typing.ParamSpec("_P")