…t_unchecked` in `Zip` `TrustedRandomAccess` specialization

Otherwise if `Iterator::self.a.__iterator_get_unchecked` panics the
index would not have been incremented yet and another call to
`Iterator::next` would read from the same index again, which is not
allowed according to the API contract of `TrustedRandomAccess` for
`!Clone`.

Fixes rust-lang#81740

Move the note about dropping cloudabi next to the other platform support
changes.

Introduced in d3c4dbd, noticed only
after the fact, sorry. 😅

Signed-off-by: Daniel Egger <daniel@eggers-club.de>

Fixes rust-lang#81928

“Ask forgiveness not permission”  : this makes the code both simpler and more robust

fix indefinite article in cell.rs

HWAddressSanitizer support

#  Motivation
Compared to regular ASan, HWASan has a [smaller overhead](https://source.android.com/devices/tech/debug/hwasan). The difference in practice is that HWASan'ed code is more usable, e.g. Android device compiled with HWASan can be used as a daily driver.

# Example
```
fn main() {
    let xs = vec![0, 1, 2, 3];
    let _y = unsafe { *xs.as_ptr().offset(4) };
}
```
```
==223==ERROR: HWAddressSanitizer: tag-mismatch on address 0xefdeffff0050 at pc 0xaaaad00b3468
READ of size 4 at 0xefdeffff0050 tags: e5/00 (ptr/mem) in thread T0
    #0 0xaaaad00b3464  (/root/main+0x53464)
    rust-lang#1 0xaaaad00b39b4  (/root/main+0x539b4)
    rust-lang#2 0xaaaad00b3dd0  (/root/main+0x53dd0)
    rust-lang#3 0xaaaad00b61dc  (/root/main+0x561dc)
    rust-lang#4 0xaaaad00c0574  (/root/main+0x60574)
    rust-lang#5 0xaaaad00b6290  (/root/main+0x56290)
    rust-lang#6 0xaaaad00b6170  (/root/main+0x56170)
    rust-lang#7 0xaaaad00b3578  (/root/main+0x53578)
    rust-lang#8 0xffff81345e70  (/lib64/libc.so.6+0x20e70)
    rust-lang#9 0xaaaad0096310  (/root/main+0x36310)

[0xefdeffff0040,0xefdeffff0060) is a small allocated heap chunk; size: 32 offset: 16
0xefdeffff0050 is located 0 bytes to the right of 16-byte region [0xefdeffff0040,0xefdeffff0050)
allocated here:
    #0 0xaaaad009bcdc  (/root/main+0x3bcdc)
    rust-lang#1 0xaaaad00b1eb0  (/root/main+0x51eb0)
    rust-lang#2 0xaaaad00b20d4  (/root/main+0x520d4)
    rust-lang#3 0xaaaad00b2800  (/root/main+0x52800)
    rust-lang#4 0xaaaad00b1cf4  (/root/main+0x51cf4)
    rust-lang#5 0xaaaad00b33d4  (/root/main+0x533d4)
    rust-lang#6 0xaaaad00b39b4  (/root/main+0x539b4)
    rust-lang#7 0xaaaad00b61dc  (/root/main+0x561dc)
    rust-lang#8 0xaaaad00b3578  (/root/main+0x53578)
    rust-lang#9 0xaaaad0096310  (/root/main+0x36310)

Thread: T0 0xeffe00002000 stack: [0xffffc0590000,0xffffc0d90000) sz: 8388608 tls: [0xffff81521020,0xffff815217d0)
Memory tags around the buggy address (one tag corresponds to 16 bytes):
  0xfefcefffef80: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffef90: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefa0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefb0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefc0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefd0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefe0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffeff0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
=>0xfefceffff000: a2  a2  05  00  e5 [00] 00  00  00  00  00  00  00  00  00  00
  0xfefceffff010: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff020: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff030: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff040: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff050: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff060: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff070: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff080: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
Tags for short granules around the buggy address (one tag corresponds to 16 bytes):
  0xfefcefffeff0: ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
=>0xfefceffff000: ..  ..  c5  ..  .. [..] ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
  0xfefceffff010: ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
See https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html#short-granules for a description of short granule tags
Registers where the failure occurred (pc 0xaaaad00b3468):
    x0  e500efdeffff0050  x1  0000000000000004  x2  0000ffffc0d8f5a0  x3  0200efff00000000
    x4  0000ffffc0d8f4c0  x5  000000000000004f  x6  00000ffffc0d8f36  x7  0000efff00000000
    x8  e500efdeffff0050  x9  0200efff00000000  x10 0000000000000000  x11 0200efff00000000
    x12 0200effe000006b0  x13 0200effe000006b0  x14 0000000000000008  x15 00000000c00000cf
    x16 0000aaaad00a0afc  x17 0000000000000003  x18 0000000000000001  x19 0000ffffc0d8f718
    x20 ba00ffffc0d8f7a0  x21 0000aaaad00962e0  x22 0000000000000000  x23 0000000000000000
    x24 0000000000000000  x25 0000000000000000  x26 0000000000000000  x27 0000000000000000
    x28 0000000000000000  x29 0000ffffc0d8f650  x30 0000aaaad00b3468
```

# Comments/Caveats
* HWASan is only supported on arm64.
* I'm not sure if I should add a feature gate or piggyback on the existing one for sanitizers.
* HWASan requires `-C target-feature=+tagged-globals`. That flag should probably be set transparently to the user. Not sure how to go about that.

# TODO
* Need more tests.
* Update documentation.
* Fix symbolization.
* Integrate with CI

…pecialization-panic-safety, r=KodrAus

Increment `self.index` before calling `Iterator::self.a.__iterator_ge…

…`t_unchecked` in `Zip` `TrustedRandomAccess` specialization

Otherwise if `Iterator::self.a.__iterator_get_unchecked` panics the
index would not have been incremented yet and another call to
`Iterator::next` would read from the same index again, which is not
allowed according to the API contract of `TrustedRandomAccess` for
`!Clone`.

Fixes rust-lang#81740

use RWlock when accessing os::env

Multiple threads modifying the current process environment is fairly uncommon. Optimize for the more common read case.

r? ``@m-ou-se``

…komatsakis

GAT/const_generics: Allow with_opt_const_param to return GAT param def_id

Fixes rust-lang#75415
Fixes rust-lang#79666
cc `@lcnr`

I've absolutely no idea who to r?  for this...

Relax ItemCtxt::to_ty lifetime

Tiny simplification by relaxing a lifetime.

…atform-notes, r=XAMPPRocky

RELEASES.md 1.50: Group platform support notes together

Move the note about dropping cloudabi next to the other platform support
changes.

bootstrap: Locate llvm-dwp based on llvm-config bindir

Fixes rust-lang#81949.

Tested by successfully building 1.50.0 pre-release, which is where I originally hit the issue (https://internals.rust-lang.org/t/rust-1-50-0-pre-release-testing/14012/4?u=dtolnay). Tested both with and without prebuilt LLVM. The check for dry_run is necessary in the non-prebuilt case because the llvm-config built by bootstrap won't exist yet.

Fix assosiated typo

Introduced in d3c4dbd, noticed only
after the fact, sorry. 😅

Signed-off-by: Daniel Egger <daniel@eggers-club.de>

Fix documentation not showing on localStorage error

Fixes rust-lang#81928

The [documentation for setItem](https://developer.mozilla.org/en-US/docs/Web/API/Storage/setItem) specifies:

> developers should make sure to always catch possible exceptions from setItem()

…r=Mark-Simulacrum

bootstrap: fix wrong docs installation path

This PR fixes rust-lang#81967, a regression introduced by rust-lang#80797. The commit has already been backported to stable 1.50.0.

r? ````@Mark-Simulacrum````

Seal the CommandExt, OsStrExt and OsStringExt traits

A crater run (rust-lang#81213 (comment)) has shown that this does not break any existing code.

This also unblocks rust-lang#77728.

Based on rust-lang#81213.

r? ``@m-ou-se``
cc ``@lygstate``