Fix MXCSR configuration dependent timing
Dependent on the (potentially secret) data some vector instructions operate on, and the content in MXCSR, instruction retirement may be delayed by one cycle. This is a potential side channel.
This PR fixes this vulnerability for the `x86_64-fortanix-unknown-sgx` platform by loading MXCSR with `0x1fbf` through an `xrstor` instruction when the enclave is entered and executing an `lfence` immediately after. Other changes of the MXCSR happen only when the enclave is about to be exited and no vector instructions will be executed before it will actually do so. Users of EDP who change the MXCSR and do wish to defend against this side channel, will need to implement the software mitigation described [here](https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/best-practices/mxcsr-configuration-dependent-timing.html).
cc: `@jethrogb` `@monokles`
Add FreeBSD cpuset support to `std:🧵:available_concurrency`
Use libc::cpuset_getaffinity to determine the CPUs available to the current process.
The existing sysconf and sysctl paths are left as fallback.
rustdoc-search: add slices and arrays to index
This indexes them as primitives with generics, so `slice<u32>` is how you search for `[u32]`, and `array<u32>` for `[u32; 1]`. A future commit will desugar the square bracket syntax to search both arrays and slices at once.
Stabilize raw-dylib, link_ordinal, import_name_type and -Cdlltool
This stabilizes the `raw-dylib` feature (#58713) for all architectures (i.e., `x86` as it is already stable for all other architectures).
Changes:
* Permit the use of the `raw-dylib` link kind for x86, the `link_ordinal` attribute and the `import_name_type` key for the `link` attribute.
* Mark the `raw_dylib` feature as stable.
* Stabilized the `-Zdlltool` argument as `-Cdlltool`.
* Note the path to `dlltool` if invoking it failed (we don't need to do this if `dlltool` returns an error since it prints its path in the error message).
* Adds tests for `-Cdlltool`.
* Adds tests for being unable to find the dlltool executable, and dlltool failing.
* Fixes a bug where we were checking the exit code of dlltool to see if it failed, but dlltool always returns 0 (indicating success), so instead we need to check if anything was written to `stderr`.
NOTE: As previously noted (https://github.com/rust-lang/rust/pull/104218#issuecomment-1315895618) using dlltool within rustc is temporary, but this is not the first time that Rust has added a temporary tool use and argument: https://github.com/rust-lang/rust/pull/104218#issuecomment-1318720482
Big thanks to ``````@tbu-`````` for the first version of this PR (#104218)
