Use shared pointer to manage PImpl object

include/linuxdeploy/core/appdir.h

@@ -1,4 +1,5 @@
 // system includes
+#include <memory>
 #include <string>
 
 // library includes
@@ -19,7 +20,7 @@ namespace linuxdeploy {
                 private:
                     // private data class pattern
                     class PrivateData;
-                    PrivateData* d;
+                    std::shared_ptr<PrivateData> d;
 
                 public:
                     // default constructor

src/core/appdir.cpp

@@ -532,15 +532,11 @@ namespace linuxdeploy {
             };
 
             AppDir::AppDir(const bf::path& path) {
-                d = new PrivateData();
+                d = std::make_shared<PrivateData>();
 
                 d->appDirPath = path;
             }
 
-            AppDir::~AppDir() {
-                delete d;
-            }
-
             AppDir::AppDir(const std::string& path) : AppDir(bf::path(path)) {}
 
             bool AppDir::createBasicStructure() {