Rust SGX SDK toolchain support status

Rust SGX SDK 1.1.4

Updated in PR: chore(web-server): update to Rust SGX SDK 1.1.4 #137

• nightly-2021-11-01 - Upstream commit: 3472e28f3ccb7ac581b53efa819e430f713ccd0a
• nightly-2021-09-13 - Upstream issue: upgrade SDK and rust compiler urgently needed #360

Rust SGX SDK 1.1.3

• nightly-2021-09-16 - ❌ Build fails (unwind_attributes, …)
• nightly-2021-06-17 - ❌ Build fails (const_fn)
• nightly-2021-05-10 - ✔️ Builds, supports 1.53 features (for semver crate)
• nightly-2021-05-06 - ✔️ Builds, supports 1.53 features (for semver crate)
• nightly-2021-03-25 - ✔️ Builds, supports 1.51 features (min_const_generics)

(These dates correspond to Rust release dates.)

(semver issues: #249, #250)