Add: '-X' option to ignore global folders in the search path (#9341)

This is extreme useful for automated testing. Without this, OpenTTD
will always look in your personal-dir (like ~/.local/share/openttd
or %USER%\Documents\OpenTTD). For most users this is exactly what
we want, that there is a shared place for all their files.

However, for automated testing this is rather annoying, as your
local development files influence the automated test. As such,
'-X' counters this, and only gives the local folders. This is
especially useful in combination with '-x' and '-c'.

src/fileio_func.h

@@ -27,7 +27,7 @@ const char *FiosGetScreenshotDir();
 
 void SanitizeFilename(char *filename);
 void AppendPathSeparator(std::string &buf);
-void DeterminePaths(const char *exe);
+void DeterminePaths(const char *exe, bool only_local_path);
 std::unique_ptr<char[]> ReadFileToMem(const std::string &filename, size_t &lenp, size_t maxsize);
 bool FileExists(const std::string &filename);
 bool ExtractTar(const std::string &tar_filename, Subdirectory subdir);