test llvm 18 for xtensa

xtensa_release_18.1.2

Author: yamt

build-scripts/build_llvm.py

@@ -299,7 +299,7 @@ def main():
         "xtensa": {
             "repo": "https://github.com/espressif/llvm-project.git",
             "repo_ssh": "git@github.com:espressif/llvm-project.git",
-            "branch": "xtensa_release_17.0.1",
+            "branch": "xtensa_release_18.1.2",
         },
         "default": {
             "repo": "https://github.com/llvm/llvm-project.git",