The main improvement is to make `last` no longer recursive.

https://sourceware.org/bugzilla/show_bug.cgi?id=22236

Rather than a boolean `--enable-cflags` etc., these options should
reflect that they are for LLVM, and that they need a value. You would
now use `./configure --llvm-cflags="..."`.

This helps us have enough disk space for our builders to be able to complete
successfully. For now, the choices are ad-hoc and 'definitely not needed'. This
should never fail the build, as everything our build needs should be inside
Docker.

…ow554

recursion_limit parsing handles overflows

This PR adds overflow handling to `#![recursion_limit]` attribute parsing. If parsing the given value results in an `IntErrorKind::Overflow`, then the recursion_limit is set to `usize::max_value()`.

closes rust-lang#67265

Simplify `Skip::nth` and `Skip::last` implementations

The main improvement is to make `last` no longer recursive.

macOS: avoid calling pthread_self() twice

Do not ICE when encountering `yield` inside `async` block

Fix rust-lang#67158.

… r=Dylan-DPC

Ignore GDB versions with broken str printing.

https://sourceware.org/bugzilla/show_bug.cgi?id=22236

configure: set LLVM flags with a value

Rather than a boolean `--enable-cflags` etc., these options should
reflect that they are for LLVM, and that they need a value. You would
now use `./configure --llvm-cflags="..."`.

…ts, r=sfackler

Stabilize {f32, f64}::{LOG2_10, LOG10_2}

Following the decision to stabilize `LOG2_10` and `LOG10_2` in rust-lang#50540 (comment).

Closes rust-lang#50540.
r? @sfackler

…lbini

Clean out unused directories for extra disk space

This cleans out some of the unused (but large) directories on our linux builders to hopefully allow them to complete without running out of disk space.