Installed Build Tools revision 31.0.0 is corrupted. Remove and install again using the SDK Manager解決方法
//通過Android studio的SDK Manager卸載然后重新下載build-tools\30.0.0和build-tools\31.0.0，確保最新的
//下載下來的build-tools\31.0.0版本是缺少dx.bat文件和lib\dx.jar文件的
//所以將build-tools\30.0.0版本的dx.bat和dx.jar分別拷貝一份到build-tools\31.0.0對應的目錄下即可解決問題
將androidSdk\build-tools\30.0.0\dx.bat 拷貝一份到 androidSdk\build-tools\31.0.0\dx.bat
將androidSdk\build-tools\30.0.0\lib\dx.jar 拷貝一份到 androidSdk\build-tools\31.0.0\lib\dx.jar