Create the datadirectory to not fail to write the aria2 session file.

Fix kiwix/kiwix-desktop#69

ChangeLog

@@ -5,6 +5,8 @@ kiwix-lib 3.1.1
  feed generation.
  * Convert the standard opds date to our format (YYYY-MM-DD)
  * Remove duplicate language attribute in the libxml dumper.
+ * Create the datadirectory to not fail to write a file in a non-existent
+   directory
 
 kiwix-lib 3.1.0
 ===============

src/aria2.cpp

@@ -26,6 +26,7 @@ Aria2::Aria2():
   m_lock(PTHREAD_MUTEX_INITIALIZER)
 {
   m_downloadDir = getDataDirectory();
+  makeDirectory(m_downloadDir);
   std::vector<const char*> callCmd;
 
   std::string rpc_port = "--rpc-listen-port=" + to_string(m_port);