[ABI Break] Correctly detect the executable path in appimage.

There are two executable path :
- The user one (the appimage path)
- The real one (in the appimage archive)

When we search of `library.xml` we need the user one.
But when we search of `aria2c` or `kiwix-serve` we need the real one.

Fix kiwix/kiwix-desktop#256

include/tools/pathTools.h

@@ -38,7 +38,7 @@ bool makeDirectory(const std::string& path);
 std::string makeTmpDirectory();
 bool copyFile(const std::string& sourcePath, const std::string& destPath);
 std::string getLastPathElement(const std::string& path);
-std::string getExecutablePath();
+std::string getExecutablePath(bool realPathOnly = false);
 std::string getCurrentDirectory();
 std::string getDataDirectory();
 bool writeTextFile(const std::string& path, const std::string& content);