Add the cmake option for flatpak.

CMakeLists.txt

@@ -25,6 +25,10 @@ if (APPLE)
     enable_language(OBJC OBJCXX)
 endif()
 
+if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+    option(RECOMP_FLATPAK "Configure the build for Flatpak compatibility." OFF)
+endif()
+
 # Avoid warning about DOWNLOAD_EXTRACT_TIMESTAMP in CMake 3.24:
 if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.24.0")
     cmake_policy(SET CMP0135 NEW)
@@ -41,6 +45,10 @@ set(RT64_STATIC TRUE)
 set(RT64_SDL_WINDOW_VULKAN TRUE)
 add_compile_definitions(HLSL_CPU)
 
+if (RECOMP_FLATPAK)
+    add_compile_definitions(RECOMP_FLATPAK)
+endif()
+
 add_subdirectory(${CMAKE_SOURCE_DIR}/lib/rt64 ${CMAKE_BINARY_DIR}/rt64)
 
 # set(BUILD_SHARED_LIBS_SAVED "${BUILD_SHARED_LIBS}")

src/main/main.cpp

@@ -602,14 +602,12 @@ int main(int argc, char** argv) {
     SDL_setenv("SDL_AUDIODRIVER", "wasapi", true);
 #endif
 
-#if 0
 #if defined(__linux__) && defined(RECOMP_FLATPAK)
     // When using Flatpak, applications tend to launch from the home directory by default.
     // Mods might use the current working directory to store the data, so we switch it to a directory
     // with persistent data storage and write permissions under Flatpak to ensure it works.
     std::error_code ec;
     std::filesystem::current_path("/var/data", ec);
-#endif
 #endif
 
     // Initialize SDL audio and set the output frequency.