Fix the Android recursive size computation and hook it up.

Core/FileSystems/DirectoryFileSystem.h

@@ -116,7 +116,7 @@ public:
 	u64 FreeSpace(const std::string &path) override;
 
 	// TODO: Replace with optimized implementation.
-	bool ComputeRecursiveDirSizeIfFast(const std::string &path, int64_t *size) override { return false; }
+	bool ComputeRecursiveDirSizeIfFast(const std::string &path, int64_t *size) override;
 
 private:
 	struct OpenFileEntry {