错误：
ERROR:Bitgen:342 - This design contains pins which have locations (LOC) that are
not user-assigned or I/O Standards (IOSTANDARD) that are not user-assigned.
This may cause I/O contention or incompatibility with the board power or
connectivity affecting performance, signal integrity or in extreme cases
cause damage to the device or the components to which it is connected. To
prevent this error, it is highly suggested to specify all pin locations and
I/O standards to avoid potential contention or conflicts and allow proper
bitstream creation. To demote this error to a warning and allow bitstream
creation with unspecified I/O location or standards, you may apply the
following bitgen switch: -g UnconstrainedPins:Allow
解决方案：