Fixed issue with new rootlogon that lead to replay compiles failing

.rootlogon.C

-#include <fmt/core.h>
+#include <string>
 
 void _rootlogon() {
   // ensure we have format loaded. Should be able to move to C++20 fmt library
@@ -13,11 +13,11 @@ void _rootlogon() {
   // note: in principle this allows us to execute arbitrary code, but seeing
   //       as this can only be manipulated through the shell environment in the
   //       first place this should not be a safety concern.
-  const std::string mkdir = fmt::format("mkdir -p {}", build_dir);
+  const std::string mkdir = "mkdir -p " + build_dir;
   gSystem->Exec(mkdir.c_str());
 
   // Communicate what build directory we are using
-  fmt::print("---> Setting ACLiC build directory to: {}\n\n", build_dir);
+  std::cout << "---> Setting ACLiC build directory to: " << build_dir << "\n\n";
   gSystem->SetBuildDir(build_dir.c_str());
 
   // Ensure we have our environment setup