VSIMkdirRecursive(): fix 1fc62d7 (master only)

Author: rouault

port/cpl_vsil.cpp

@@ -647,8 +647,12 @@ int VSIMkdirRecursive(const char *pszPathname, long mode)
     if (!pszPathname)
         return -1;
 
-    const std::string osPathnameOri(VSIFileManager::GetHandler(pszPathname)
-                                        ->GetCanonicalFilename(pszPathname));
+    std::string osPathnameOri(pszPathname);
+    if (cpl::starts_with(osPathnameOri, "/vsimem/"))
+    {
+        osPathnameOri = VSIFileManager::GetHandler(pszPathname)
+                            ->GetCanonicalFilename(osPathnameOri);
+    }
     // Limit to avoid performance issues such as in
     // https://issues.oss-fuzz.com/issues/471096341
     constexpr size_t CPL_MAX_PATH = 4096;