util/zippath.cpp: OSD_WINDOWS isn't a safe way to detect Windows targ…

…et, and OSD_* macros must not be used outside libocore/libosd.

src/lib/util/zippath.cpp

@@ -48,14 +48,17 @@ int is_path_separator(char c)
 
 bool is_root(std::string_view path)
 {
-#if defined(OSD_WINDOWS)
+#if defined(WIN32)
+	// FIXME: don't assume paths are DOS-like - UNC paths, \\?\ long path prefix, etc. complicate this
+
 	// skip drive letter
 	if (path.length() >= 2 && isalpha(path[0]) && (path[1] == ':'))
 		path.remove_prefix(2);
 
 	// skip path separators
 	return path.find_first_not_of(PATH_SEPARATOR) == std::string_view::npos;
 #else
+	// FIXME: handle multiple successive path separators, current directory references, parent directory references
 	return (path.length() == 1) && (path[0] == '/');
 #endif
 }