Create save and config directories

If a config directory did not exist, the ini file was
not saved at all.

Only implemented for targets that support `std::filesystem` or `std::experimental::filesystem`.
These are all the targets except nxdk and iOS (only supported on iOS 13+).

CMake/functions/set_relative_file_macro.cmake

@@ -1,7 +1,7 @@
 # Sets the __FILE__ macro value to be relative to CMAKE_SOURCE_DIR.
 function(set_relative_file_macro TARGET)
   if(NOT CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
-    if((CMAKE_CXX_COMPILER_ID MATCHES "CLANG" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12)
+    if((CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12)
         OR (CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 8))
       target_compile_options(${TARGET} PUBLIC "-fmacro-prefix-map=${CMAKE_SOURCE_DIR}/=")
     else()

Source/CMakeLists.txt

@@ -288,3 +288,17 @@ foreach(path ${DEVILUTIONX_PLATFORM_SUBDIRECTORIES})
 endforeach()
 
 target_link_libraries(libdevilutionx PUBLIC ${DEVILUTIONX_PLATFORM_LINK_LIBRARIES})
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+  if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9 AND NOT AMIGA)
+    target_link_libraries(libdevilutionx PUBLIC stdc++fs)
+  endif()
+elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  # Assumes libc++ (clang) is used rather than libstdc++ (gcc).
+  # This is not always true but these are ancient clang versions anyway.
+  if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7)
+    target_link_libraries(libdevilutionx PUBLIC c++experimental)
+  elseif(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9)
+    target_link_libraries(libdevilutionx PUBLIC c++fs)
+  endif()
+endif()

Source/mpq/mpq_writer.cpp

@@ -13,6 +13,7 @@
 #include "utils/file_util.h"
 #include "utils/language.h"
 #include "utils/log.hpp"
+#include "utils/stdcompat/filesystem.hpp"
 #include "utils/str_cat.hpp"
 
 namespace devilution {
@@ -87,6 +88,15 @@ bool IsUnallocatedBlock(const MpqBlockEntry *block)
 
 MpqWriter::MpqWriter(const char *path)
 {
+#ifdef DVL_HAS_FILESYSTEM
+	{
+		std::error_code error;
+		std::filesystem::create_directories(std::filesystem::path(path).parent_path(), error);
+		if (error) {
+			LogError("failed to create directory: {}", error.message());
+		}
+	}
+#endif
 	LogVerbose("Opening {}", path);
 	std::string error;
 	bool exists = FileExists(path);

Source/options.cpp

@@ -31,6 +31,7 @@
 #include "utils/log.hpp"
 #include "utils/paths.h"
 #include "utils/stdcompat/algorithm.hpp"
+#include "utils/stdcompat/filesystem.hpp"
 #include "utils/str_cat.hpp"
 #include "utils/str_split.hpp"
 #include "utils/utf8.hpp"
@@ -234,6 +235,15 @@ void SaveIni()
 {
 	if (!IniChanged)
 		return;
+#ifdef DVL_HAS_FILESYSTEM
+	{
+		std::error_code error;
+		std::filesystem::create_directories(paths::ConfigPath(), error);
+		if (error) {
+			LogError("failed to create directory: {}", error.message());
+		}
+	}
+#endif
 	auto iniPath = GetIniPath();
 	auto stream = CreateFileStream(iniPath.c_str(), std::fstream::out | std::fstream::trunc | std::fstream::binary);
 	GetIni().Save(*stream, true);

Source/utils/stdcompat/filesystem.hpp

@@ -0,0 +1,24 @@
+#pragma once
+
+#if defined(__APPLE__)
+#include <Availability.h>
+#if (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED < 101500) \
+    || (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED < 130000)
+#define DVL_NO_FILESYSTEM
+#endif
+#elif defined(NXDK) || (defined(_MSVC_LANG) && _MSVC_LANG < 201703L)
+#define DVL_NO_FILESYSTEM
+#endif
+
+#ifndef DVL_NO_FILESYSTEM
+#if defined(__has_include)
+#if __has_include(<filesystem>)
+#define DVL_HAS_FILESYSTEM
+#include <filesystem> // IWYU pragma: export
+#elif __has_include(<experimental/filesystem>)
+#define DVL_HAS_FILESYSTEM
+#include <experimental/filesystem> // IWYU pragma: export
+#define filesystem experimental::filesystem
+#endif
+#endif
+#endif