Linux build system: server-only target + portable warnings

- CMakeLists: allow Linux 64-bit, server-only includes, portable tests
- ProjectOptions: MSVC /W4 vs GCC -Wall, version.rc Windows-only
- Core/Dependencies: guard Windows-only libs, OpenSSL for launcher_support
- Apps: launcher/emote Windows-only, server Linux links OpenSSL/dl/pthread
- Fix launcher_support lambda return, cas_codec Oodle guards, steam dlerror crash

Engine/Resource/cas_codec.cpp

@@ -84,7 +84,7 @@ template <typename Function> Function oodle_function(const std::filesystem::path
 #else
 // Linux dedicated servers read pre-exported world-layers.json; Oodle blocks
 // (game CAS) need the Windows game + oo2core DLL and are unsupported here.
-void *oodle(const std::filesystem::path &) {
+[[maybe_unused]] void *oodle(const std::filesystem::path &) {
     throw std::runtime_error("Oodle CAS data is only supported on Windows (export world-layers.json there)");
 }
 template <typename Function> Function oodle_function(const std::filesystem::path&, const char* name) {
@@ -127,6 +127,7 @@ std::vector<std::byte> zstd_decode(std::span<const std::byte> input, std::size_t
 
 std::vector<std::byte> oodle_decode(std::span<const std::byte> input, std::size_t size,
                                     const std::filesystem::path& gameRoot) {
+#ifdef _WIN32
     using Function = std::int64_t(__cdecl*)(const void*, std::int64_t, void*, std::int64_t, int, int,
                                             int, void*, std::int64_t, void*, void*, void*, std::int64_t, int);
     const auto decode = oodle_function<Function>(gameRoot, "OodleLZ_Decompress");
@@ -136,10 +137,17 @@ std::vector<std::byte> oodle_decode(std::span<const std::byte> input, std::size_
                nullptr, 0, 3) != static_cast<std::int64_t>(size))
         throw std::runtime_error("Oodle CAS block failed to decode");
     return output;
+#else
+    (void)input;
+    (void)size;
+    (void)gameRoot;
+    throw std::runtime_error("Oodle CAS data is only supported on Windows (export world-layers.json there)");
+#endif
 }
 
 std::vector<std::byte> oodle_encode(std::span<const std::byte> input, CasCompression compression,
                                     int level, const std::filesystem::path& gameRoot) {
+#ifdef _WIN32
     using Bound = std::int64_t(__cdecl*)(int, std::int64_t);
     using Compress = std::int64_t(__cdecl*)(int, const void*, std::int64_t, void*, int, void*, void*,
                                             void*, void*, std::int64_t);
@@ -160,6 +168,13 @@ std::vector<std::byte> oodle_encode(std::span<const std::byte> input, CasCompres
     if (length <= 0 || length > capacity) throw std::runtime_error("Oodle CAS compression failed");
     output.resize(static_cast<std::size_t>(length));
     return output;
+#else
+    (void)input;
+    (void)compression;
+    (void)level;
+    (void)gameRoot;
+    throw std::runtime_error("Oodle CAS data is only supported on Windows");
+#endif
 }
 
 std::vector<std::byte> read_block(Cursor& cursor, const CasDecodeOptions& options) {