apps fail to build since NDK update to r17 (due to missing mipsel-linux-android-4.9 toolchain files)

图片发自App

当MacOS上的android studio升级ndk到17时，报错：

To work around this, our team had to manually replace the bare NDK r17 ~/Library/Android/sdk/ndk-bundle/toolchains/mips64el-linux-android-4.9/ and ~/Library/Android/sdk/ndk-bundle/toolchains/mipsel-linux-android-4.9/ directories with those of the old NDK r16. Almost all files that were once in these 2 directories bacvk in NDK r16 are completely gone in the new NDK r17

解决办法（https://github.com/android-ndk/ndk/issues/700）