LibCore: Add S_ISDIR, S_ISREG to System.h on Windows

Before this commit, LibCore/System.h exposed only part of
System::stat API on Windows. Namely, users of Core::System::stat
had to #include <dirent.h> in order to check the return value of stat.
It is OK for low-level libs like LibCore/LibFileSystem, but
S_ISDIR is also used in LibWeb\Loader\GeneratedPagesLoader.cpp.
We want to avoid platform #ifdefs in LibWeb.

Libraries/LibCore/ResourceImplementation.cpp

@@ -9,10 +9,6 @@
 #include <LibCore/ResourceImplementationFile.h>
 #include <LibCore/System.h>
 
-#if defined(AK_OS_WINDOWS)
-#    include <dirent.h>
-#endif
-
 namespace Core {
 
 static OwnPtr<ResourceImplementation> s_the;

Libraries/LibCore/ResourceImplementationFile.cpp

@@ -11,10 +11,6 @@
 #include <LibCore/ResourceImplementationFile.h>
 #include <LibCore/System.h>
 
-#if defined(AK_OS_WINDOWS)
-#    include <dirent.h>
-#endif
-
 namespace Core {
 
 ResourceImplementationFile::ResourceImplementationFile(String base_directory)

Libraries/LibCore/System.h

@@ -33,6 +33,8 @@
 #    include <utime.h>
 #else
 #    define O_CLOEXEC O_NOINHERIT
+#    define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
+#    define S_ISREG(mode) (((mode) & S_IFMT) == S_IFREG)
 using sighandler_t = void (*)(int);
 using socklen_t = int;
 #endif

Libraries/LibFileSystem/CMakeLists.txt

@@ -5,8 +5,3 @@ endif()
 
 serenity_lib(LibFileSystem filesystem)
 target_link_libraries(LibFileSystem PRIVATE LibCoreMinimal)
-
-if (WIN32)
-    find_path(DIRENT_INCLUDE_DIR dirent.h REQUIRED)
-    target_include_directories(LibFileSystem PRIVATE ${DIRENT_INCLUDE_DIR})
-endif()

Libraries/LibFileSystem/FileSystem.cpp

@@ -16,7 +16,7 @@
 #elif defined(AK_OS_LINUX)
 #    include <linux/fs.h>
 #elif defined(AK_OS_WINDOWS)
-#    include <dirent.h>
+#    include <windows.h>
 #endif
 
 // On Linux distros that use glibc `basename` is defined as a macro that expands to `__xpg_basename`, so we undefine it