message: always build AsyncIo and IoUring sources
  Summary: Their contents may be preprocessed away if the corresponding platform headers are unavailable. But this removes some of the build-time and build-config complexity.
diff: #include <quic/server/QuicServer.h>
  -#if defined(__linux__) && !FOLLY_MOBILE && __has_include(<liburing.h>) && \
  - __has_include(<folly/experimental/io/IoUringBackend.h>)
  #include <folly/experimental/io/IoUringBackend.h>
  +#if !FOLLY_MOBILE && __has_include(<liburing.h>)
  +
  DEFINE_int32(
  qs_io_uring_capacity,
  -1,
  @@ -46,10 +46,13 @@ std::unique_ptr<folly::EventBaseBackendBase> QuicServer::getEventBaseBackend() {
  return folly::EventBase::getDefaultBackend();
  }
  } // namespace quic
  +
  #else
  +
  namespace quic {
  std::unique_ptr<folly::EventBaseBackendBase> getEventBaseBackend() {
  return folly::EventBase::getDefaultBackend();
  }
  } // namespace quic
  +
  #endif
  