compat.spdlog

// Behavioral test: consume compat.spdlog in COMPILED mode. Asserts both halves
// of what the `compiled` feature promises:
//
//   1. the interface define reached this TU (SPDLOG_COMPILED_LIB defined, and
//      spdlog's headers therefore did NOT flip on SPDLOG_HEADER_ONLY) — a
//      static check, so a regression is a compile error, not a silent fallback
//      to the header-only path that would still pass the runtime assertions;
//   2. spdlog's src/*.cpp really were compiled and linked — the calls below
//      resolve to out-of-line symbols (default_logger_raw, log_msg's ctor,
//      logger::log_it_, and bundled fmt's vformat), which is exactly what fails
//      to link when the engine skips a feature's sources.
#include <spdlog/spdlog.h>
#include <spdlog/sinks/ostream_sink.h>
#include <sstream>
#include <string>

#ifndef SPDLOG_COMPILED_LIB
#error "compiled feature did not propagate SPDLOG_COMPILED_LIB to the consumer"
#endif
#ifdef SPDLOG_HEADER_ONLY
#error "SPDLOG_HEADER_ONLY is on in compiled mode — headers took the inline path"
#endif
// …