How to get polarssl during compiling OpenLTE?

There is no "polarssl" any more, its name is changed to mbedtls.

You can download older tarball and compile it by yourself.

Please refer to below links:

https://tls.mbed.org/download-archive     // Get older polarssl

https://tls.mbed.org/kb/compiling-and-building/how-do-i-build-compile-mbedtls      // Show you how to compile