Before:
```
LD_LIBRARY_PATH="/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/lib:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0-bootstrap-tools/aarch64-unknown-linux-gnu/release/deps:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0/lib" '/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/bin/rustc' --out-dir /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation -L /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation  test.rs --sysroot /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation/fakeroot -Ztranslate-lang=zh-CN 2>&1 | grep "this is a test message"
------------------------------------------
--- stderr -------------------------------
make: *** [Makefile:51: sysroot] Error 1
------------------------------------------

failures:
    [run-make] tests/run-make/translation
```

After:

```
LD_LIBRARY_PATH="/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/lib:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0-bootstrap-tools/aarch64-unknown-linux-gnu/release/deps:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0/lib" '/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/bin/rustc' --out-dir /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation -L /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation  test.rs --sysroot /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation/fakeroot -Ztranslate-lang=zh-CN 2>&1 | grep "this is a test message"
[[[ begin stdout ]]]
error: failed to load fluent bundle: failed to add resource: Attempt to override an existing message: "parse_struct_literal_body_without_path".

[[[ end stdout ]]]
Error: cannot match: this is a test message
------------------------------------------
--- stderr -------------------------------
make: *** [Makefile:51: sysroot] Error 1
------------------------------------------

failures:
    [run-make] tests/run-make/translation
```

We don't support old versions of LLVM; there's no reason to have an easy
way to force bootstrap to use them anyway. If someone really needs to
use an unsupported version, they can modify bootstrap to change the
version range.

Remove the option to disable `llvm-version-check`

We don't support old versions of LLVM; there's no reason to have an easy way to force bootstrap to use them anyway. If someone really needs to use an unsupported version, they can modify bootstrap to change the version range.

r? ``@cuviper`` on whether we want to do this or not, since you maintain rust on Fedora and touched this config last.

…lwoerister

infer: fix and improve comments

…ture, r=petrochenkov

feat: impl better help for `.poll()` not found on `impl Future`

Partially address rust-lang#108572

I'd like to also address suggestions for generalized `Self` parameters as well. That'll be a separate PR.

…twco

Greatly improve the error messages when `run-make/translation` fails

Before:
```
LD_LIBRARY_PATH="/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/lib:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0-bootstrap-tools/aarch64-unknown-linux-gnu/release/deps:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0/lib" '/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/bin/rustc' --out-dir /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation -L /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation  test.rs --sysroot /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation/fakeroot -Ztranslate-lang=zh-CN 2>&1 | grep "this is a test message"
------------------------------------------
--- stderr -------------------------------
make: *** [Makefile:51: sysroot] Error 1
------------------------------------------

failures:
    [run-make] tests/run-make/translation
```

After:

```
LD_LIBRARY_PATH="/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/lib:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0-bootstrap-tools/aarch64-unknown-linux-gnu/release/deps:/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage0/lib" '/home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/stage2/bin/rustc' --out-dir /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation -L /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation  test.rs --sysroot /home/gh-jyn514/rust/build/aarch64-unknown-linux-gnu/test/run-make/translation/translation/fakeroot -Ztranslate-lang=zh-CN 2>&1 | grep "this is a test message"
[[[ begin stdout ]]]
error: failed to load fluent bundle: failed to add resource: Attempt to override an existing message: "parse_struct_literal_body_without_path".

[[[ end stdout ]]]
Error: cannot match: this is a test message
------------------------------------------
--- stderr -------------------------------
make: *** [Makefile:51: sysroot] Error 1
------------------------------------------

failures:
    [run-make] tests/run-make/translation
```

…triddle

Update askama to 0.12 and improve whitespace control

`askama` 0.12 was just released, and it adds the possibility to have "whitespace suppression" enabled by default in the configuration so I switched to it.

r? ``@notriddle``

…king_issue, r=Nilstrieb

Add tracking issue for cf-protection to unstable book

Custom MIR: Support `as` casts

Small changes to support this low hanging fruit

r? `@oli-obk` or `@tmiasko` or `@JakobDegen`