Created by: chen-zhiyu

PR types

New features

PR changes

Others

Describe

to support port paddle to libos-like SGX TEE enironment, which used musl as basic libc runtime. currently supported scone and occlum, and graphene is under working.

1. add with_musl compile option
2. fix problem in quering libc version
3. add macro to disable involved the backtrace(which is not valid in musl) when with_musl=on
4. upgrade protobuf from 3.1.0 to 3.5.0, to fix the bswap_* function redefined in probuff lib when with_crypto is enabled.