Build: add support to libxc 6. (#1711)

Author: caic99

CMakeLists.txt

@@ -322,7 +322,7 @@ if(DEFINED Libxc_DIR)
   set(ENABLE_LIBXC ON)
 endif()
 if(ENABLE_LIBXC)
-  find_package(Libxc 5.1.7 REQUIRED HINTS ${Libxc_DIR}/share/cmake/Libxc)
+  find_package(Libxc 5.1.7 REQUIRED HINTS ${Libxc_DIR}/share/cmake/Libxc ${Libxc_DIR}/lib/cmake/Libxc)
   if(${Libxc_FOUND})
     message(STATUS "Found Libxc: version " ${Libxc_VERSION})
     target_link_libraries(${ABACUS_BIN_NAME} Libxc::xc)