Add libunwind to update scripts (#20091)

- Add libunwind to `push_llvm_changes.py`
- Add `update_libunwind.py`

Author: aheejin

system/lib/push_llvm_changes.py

@@ -21,6 +21,7 @@
   'compiler-rt',
   'libcxx',
   'libcxxabi',
+  'libunwind',
 ]
 
 

system/lib/update_libunwind.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+# Copyright 2023 The Emscripten Authors.  All rights reserved.
+# Emscripten is available under two separate licenses, the MIT license and the
+# University of Illinois/NCSA Open Source License.  Both these licenses can be
+# found in the LICENSE file.
+
+import os
+import sys
+import shutil
+
+script_dir = os.path.abspath(os.path.dirname(__file__))
+emscripten_root = os.path.dirname(os.path.dirname(script_dir))
+default_llvm_dir = os.path.join(os.path.dirname(emscripten_root), 'llvm-project')
+local_root = os.path.join(script_dir, 'libunwind')
+local_src = os.path.join(local_root, 'src')
+local_inc = os.path.join(local_root, 'include')
+
+
+def main():
+  if len(sys.argv) > 1:
+    llvm_dir = os.path.join(os.path.abspath(sys.argv[1]))
+  else:
+    llvm_dir = default_llvm_dir
+  upstream_root = os.path.join(llvm_dir, 'libunwind')
+  upstream_src = os.path.join(upstream_root, 'src')
+  upstream_inc = os.path.join(upstream_root, 'include')
+  assert os.path.exists(upstream_inc)
+  assert os.path.exists(upstream_src)
+
+  # Remove old version
+  shutil.rmtree(local_src)
+  shutil.rmtree(local_inc)
+
+  shutil.copytree(upstream_src, local_src)
+  shutil.copytree(upstream_inc, local_inc)
+  shutil.copy2(os.path.join(upstream_root, 'LICENSE.TXT'), local_root)
+
+
+if __name__ == '__main__':
+  main()