…or to allow unsized T.

we now distinguish between pidfd_spawn support, pidfd-via-fork/exec and not-supported

`Config::src` already contains the top-level path, so we don't need to
add git overhead just to reach this path.

Signed-off-by: onur-ozkan <[email protected]>

binutils 2.40 is required by LLVM 19, as older versions do not
know about the zmmull extension.

I've had to backport some patches to glibc and gcc as well,
as they don't build with binutils 2.40. Alternatively, we could
also switch to glibc 2.35 and gcc 12 (I think). I figured we'd
want to avoid the glibc version change, but if that's fine for
riscv I can go with that instead.

A `rustc_const_stable` attribute by itself has nonintuitive purpose when
placed in a public module.

Separately, it would probably be okay to rename `const_strlen` to just
`strlen` to make it more clear this is our general-purpose
implementation of strlen now, not something specifically for const
(avoiding confusion like in PR 127444).

The previous value, 10 hours, is unnecessarily long, since most of our jobs finish within 2.5 hours currently.

fully move it into `rustc_type_ir` and make it
independent of `Interner`.

Generalize `fn allocator` for Rc/Arc.

Split out from rust-lang#119761

- For `Rc`/`Arc`, the existing associated `fn`s are changed to allow unsized pointees.
 - For `Weak`s, new methods are added.

`````@rustbot````` label  A-allocators

Add AMX target-features and `x86_amx_intrinsics` feature flag

This is an effort towards rust-lang#126622. This adds support for all 5 target-features for `AMX`, and introduces the feature flag `x86_amx_intrinsics`, which would gate these target-features and the yet-to-be-implemented amx intrinsics in stdarch.

Use pidfd_spawn for faster process spawning when a PidFd is requested

glibc 2.39 added `pidfd_spawnp` and `pidfd_getpid` which makes it possible to get pidfds while staying on the CLONE_VFORK path.

verified that vfork gets used with strace:

```
$  strace -ff -e pidfd_open,clone3,openat,execve,waitid,close ./x test std --no-doc -- pidfd
[...]
[pid 2820532] clone3({flags=CLONE_VM|CLONE_PIDFD|CLONE_VFORK|CLONE_CLEAR_SIGHAND, pidfd=0x7b7f885fec6c, exit_signal=SIGCHLD, stack=0x7b7f88aff000, stack_size=0x9500}strace: Process 2820533 attached
 <unfinished ...>
[pid 2820533] execve("/home/the8472/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */) = -1 ENOENT (No such file or directory)
[pid 2820533] execve("/home/the8472/.cargo/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */) = -1 ENOENT (No such file or directory)
[pid 2820533] execve("/usr/local/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */) = -1 ENOENT (No such file or directory)
[pid 2820533] execve("/usr/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */ <unfinished ...>
[pid 2820532] <... clone3 resumed> => {pidfd=[3]}, 88) = 2820533
[pid 2820533] <... execve resumed>)     = 0
[pid 2820532] openat(AT_FDCWD, "/proc/self/fdinfo/3", O_RDONLY|O_CLOEXEC) = 4
[pid 2820532] close(4)                  = 0
```

Tracking issue: rust-lang#82971

Stabilize const_cstr_from_ptr (CStr::from_ptr, CStr::count_bytes)

Completed the pair of FCPs rust-lang#113219 (comment)   rust-lang#114441 (comment).

`CStr::from_ptr` is covered by just the first FCP on its own. `CStr::count_bytes` requires the approval of both FCPs. The second paragraph of the first link and the last paragraph of the second link explain the relationship between the two FCPs. As both have been approved, we can proceed with stabilizing `const` on both of these already-stable functions.

…r=Kobzol

remove unnecessary `git` usages

`Config::src` already contains the top-level path, so we don't need to add git overhead just to reach this path.

Update dist-riscv64-linux to binutils 2.40

binutils 2.40 is required by LLVM 19, as older versions do not know about the zmmul extension.

I've had to backport some patches to glibc and gcc as well, as they don't build with binutils 2.40. Alternatively, we could also switch to glibc 2.35 and gcc 10 (I think). I figured we'd want to avoid the glibc version change, but if that's fine for riscv I can go with that instead.

r? `````@cuviper`````

try-job: dist-riscv64-linux

…r-errors

generalize search graph to enable fuzzing

I do not believe it to be feasible to correctly implement the search graph without fuzzing. This PR enables this by requiring a fuzzer to only implement three new traits:
- `Cx`: implemented by all `I: Interner`
- `ProofTreeBuilder`: implemented by `struct ProofTreeBuilder<D>` for all `D: SolverDelegate`
- `Delegate`: implemented for a new `struct SearchGraphDelegate<D>` for all `D: SolverDelegate`

It also moves the evaluation cache implementation into `rustc_type_ir`, requiring `Interner` to provide methods to create and access arbitrary `WithDepNode<T>` and to provide mutable access to a given `GlobalCache`. It otherwise does not change the API surface for users of the shared library.

This change should not impact behavior in any way.

r? ``@compiler-errors``

…lbini

Lower timeout of CI jobs to 4 hours

The previous value, 10 hours, is unnecessarily long, since most of our jobs finish within 2.5 hours currently. This could help us detect abnormally long CI runs.

r? ``@pietroalbini``