Refactoring louloulibs and cmake

Use OBJECT libraries
Remove the louloulibs directory
Write FOUND variables in the cache

src/utils/xdg.cpp

@@ -0,0 +1,29 @@
+#include <utils/xdg.hpp>
+#include <cstdlib>
+
+#include "biboumi.h"
+
+std::string xdg_path(const std::string& filename, const char* env_var)
+{
+  const char* xdg_home = ::getenv(env_var);
+  if (xdg_home && xdg_home[0] == '/')
+    return std::string{xdg_home} + "/" PROJECT_NAME "/" + filename;
+  else
+    {
+      const char* home = ::getenv("HOME");
+      if (home)
+        return std::string{home} + "/" ".config" "/" PROJECT_NAME "/" + filename;
+      else
+        return filename;
+    }
+}
+
+std::string xdg_config_path(const std::string& filename)
+{
+  return xdg_path(filename, "XDG_CONFIG_HOME");
+}
+
+std::string xdg_data_path(const std::string& filename)
+{
+  return xdg_path(filename, "XDG_DATA_HOME");
+}