If you don't want to update your gradle plugin you can do this. Download one of the older NDK releases, e.g. r17c. Open downloaded NDK archive, go to toolchains directory and copy missing toolchain folders to toolchains folder of your currently used NDK. In my case the folders I had to copy were mipsel-linux-android-4.9 and mips64el-linux-android-4.9.
