Linux build improvements (#843)

- **Sentry crashpad patch**: Make static libc++ linking conditional on `-stdlib=libc++` being active, so the patch doesn't break gcc or system clang builds that use libstdc++
- **GCC warning fix**: Suppress `-Wunused-but-set-variable` for gcc (false positive with `constinit` static locals passed by reference)
- **ASIO typo fix**: `ASIO_STANDLONE` → `ASIO_STANDALONE`
- **Toolchain verification script**: `scripts/ue_build_linux/verify_linux_toolchains.sh` for testing builds across gcc, ue-clang, clang-19 and clang-20

1 files changed, 1 insertions, 1 deletions

diff --git a/thirdparty/asio/asio/include/asio/detail/io_uring_service.hpp b/thirdparty/asio/asio/include/asio/detail/io_uring_service.hpp
index 7cc6cc51b..f76ac953a 100644
--- a/thirdparty/asio/asio/include/asio/detail/io_uring_service.hpp
+++ b/thirdparty/asio/asio/include/asio/detail/io_uring_service.hpp
@@ -50,7 +50,7 @@ private:
 public:
   enum op_types { read_op = 0, write_op = 1, except_op = 2, max_ops = 3 };
 
-  class io_object;
+  struct io_object;
 
   // An I/O queue stores operations that must run serially.
   class io_queue : operation