Reproducible build for Publicly verifiable attestation

Given our multi-party settings, no single entity can be trusted to build the enclaves which are attested to. Assuming open source, the easiest approach is reproducible build. SGX SDK 2.6, has started to add support to build SDK and samples reproducibly based, see https://github.com/intel/linux-sgx/tree/master/linux/docker. Hopefully we will be able to leverage that to reproducibly build
- ecc shim library
- ltcc
and facilitate
- fpc ecc enclave reproducible build