Using std Aware Cargo

"std Aware Cargo" (https://github.com/rust-lang/wg-cargo-std-aware) is one of the most important building blocks for Teaclave SGX SDK. With this, we can build SGX enclave without worry about the complexity brought by Xargo or no-std Cargo. However this is a long-term plan for Cargo, which doesn't gain higher priority from the community.

Recently, I found that they already has an MVP implementation (https://github.com/rust-lang/wg-cargo-std-aware#mvp-implementation). This supports an option called `build-std` to build std/core/compiler-builtins from sources. However, the MVP implementation only partially solves our issue. I didn't see any further plan further.

However, I found the `build-std` option may good enough for us. I created a repository to show the possibility of using it: https://github.com/mssun/build-std.

If you're interested in this, please help me to figure out if there're any potential difficulties of using `build-std`.

Start by reviewing the linked std Aware Cargo MVP documentation and the build-std repository mentioned in the issue. Investigate whether build-std can support the Teaclave SGX SDK use case and identify potential difficulties. Done means a concrete feasibility assessment with the relevant limitations documented.

Written by the indexing model from the issue text.