Fix esp-idf-sys#278

[ivmarkov]

@MabezDev This is fixing this issue in esp-idf-sys.

The TL;DR is that xtensa GCC aligns 64 and 128 bit values at the 4 byte boundary, while our rust xtensa targets align these at their default, i.e. at the 8 and 16th byte boundary, which leads to rust panicking at runtime if it finds a GCC-provided structure, which - from its POV - is misaligned.

The fix is simply aligning (pun intended) the Rust/LLVM alignment spec with the one in xtensa GCC.

While this is crucial for the esp-idf-* crates (and therefore the -espidf targets), I suspect it might be a thing for the baremetal targets too, considering the WIFI and BLE blobs, as well as the mbed-tls usage on baremetal (whatever the status of that last project is).

Hence I touched these too.

Let me know if I have to rebase the PR against a different branch. Not really sure what is the git workflow policy of the esp-rs Rust fork these days.

[ivmarkov]

Just to mention that I just noticed the only other open PR against esp-rs which happens to be on the exact same issue. Let me go through it...

[ivmarkov]

Closing in favor of #195