Enable Installation of Python Package with System lib in a Virtual Environment (#9349)

python-package/xgboost/libpath.py

@@ -27,7 +27,7 @@ def find_lib_path() -> List[str]:
         os.path.join(curr_path, os.path.pardir, os.path.pardir, "lib"),
         # use libxgboost from a system prefix, if available.  This should be the last
         # option.
-        os.path.join(sys.prefix, "lib"),
+        os.path.join(sys.base_prefix, "lib"),
     ]
 
     if sys.platform == "win32":
@@ -62,8 +62,8 @@ def find_lib_path() -> List[str]:
             + ("\n- ".join(dll_path))
             + "\nXGBoost Python package path: "
             + curr_path
-            + "\nsys.prefix: "
-            + sys.prefix
+            + "\nsys.base_prefix: "
+            + sys.base_prefix
             + "\nSee: "
             + link
             + " for installing XGBoost."