Update LIBUNWIND_ENABLE_WERROR default value in BuildingLibunwind.rst (#135546)

`LIBUNWIND_ENABLE_WERROR` defaults to `OFF` according to
[CMakeLists.txt](https://github.com/llvm/llvm-project/blob/main/libunwind/CMakeLists.txt#L43).

GitOrigin-RevId: dd107b20daedbc49dc3003ae2cb2e846267c308c
1 file changed
tree: bde2aec65ff76a7078e1b0e2515d498fedeb73ce
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT