Change cleaning strategy of output path

opSimulation changed the strategy how to deal with the output path by making sure that it is completely empty before starting the simulation. This has been done by removing and recreating the output path. Under Linux this behavior is a problem as it destroys symbolic links, and then recreated them as actual directories. This commit changes the behavior of the cleanup by just removing the content of the given output path instead of recreating.

sim/src/core/opSimulation/framework/main.cpp

@@ -199,25 +199,55 @@ void SetupLogging(const std::filesystem::path& executionPath, LogLevel logLevel,
   LOG_INTERN(LogLevel::DebugCore) << "\n\n### simulation start ##";
 }
 
-bool PrepareDirectoriesAndLogging(const openpass::core::Directories& directories,
-                                  LogLevel logLevel,
-                                  const std::string& logFileString)
+/// @brief Removes all files and directories in the given directory
+/// @param dir path to the directory, which shall be cleared (recursive)
+/// @returns true on success, false on errors (reported to cerr)
+bool ClearDir(const std::filesystem::path& dir) [[nothrow]]
 {
   namespace fs = std::filesystem;
 
+  auto reportError = [](const fs::path& dir, const std::string& additionalInfo)
+  { std::cerr << "Failed to clean \"" << dir.string() << "\": " << additionalInfo << '\n'; };
+
   try
   {
-    fs::remove_all(directories.outputDir);
-    fs::create_directories(directories.outputDir);
+    fs::create_directory(dir);
+    for (const auto& entry : fs::directory_iterator(dir))
+    {
+      fs::remove_all(entry.path());
+    }
+    if (!fs::is_empty(dir))
+    {
+      reportError(dir, "Path not empty after calling \"remove_all\".");
+      return false;
+    }
   }
   catch (const fs::filesystem_error& e)
   {
-    throw std::runtime_error(std::string("Error when cleaning output path - ") + e.what());
+    reportError(dir, e.what());
+    return false;
   }
 
+  return true;
+}
+
+/// @brief Prepare directories and logging
+/// @param directories    Directories use by the simulator
+/// @param logLevel       Selected Loglevel
+/// @param logFileString  Path to the logfile
+/// @returns true on success, false on error
+bool PrepareDirectoriesAndLogging(const openpass::core::Directories& directories,
+                                  LogLevel logLevel,
+                                  const std::string& logFileString)
+{
   // Setup is done after the output directory has been cleaned
   // for the case that logFileString is set to the output folder
   // itself, preventing proper cleanup of the output folder
+  if (!ClearDir(directories.outputDir))
+  {
+    return false;
+  }
+
   SetupLogging(directories.baseDir, logLevel, logFileString);
   LOG_INTERN(LogLevel::DebugCore) << "base path: " << directories.baseDir;
   LOG_INTERN(LogLevel::DebugCore) << "library path: " << directories.libraryDir;