10.10 is out, so it's weird to see a message that says you're on 10.9.
Change the message to be >=10.9.

Then, decouple the question of whether the compiler/stdlib carry
debuginfo (which is controlled via `--enable-debuginfo` and implied by
`--enable-debug`) from the question of whether the tests carry
debuginfo (which now no longer is implied by `--enable-debug` nor
`--enable-debuginfo`, and is off by default).

This commit adds support to the makefiles, configuration script, and build
system to understand MUSL. This is broken up into a few parts:

* Any target of the form `*-musl` requires the `--musl-root` option to
  `./configure` which will indicate the root of the MUSL installation. It is
  also expected that there is a libunwind build inside of that installation
  built against that MUSL.

* Objects from MUSL are copied into the build tree for Rust to be statically
  linked into the appropriate Rust library.

* Objects for binary startup and shutdown are included in each Rust installation
  by default for MUSL. This requires MUSL to only be installed on the machine
  compiling rust. Only a linker will be necessary for compiling against MUSL on
  a target machine.

Eventually a MUSL and/or libunwind build may be integrated by default into the
build but for now they are just always assumed to exist externally.

In most places in mk/tests.mk, it's positioned after rpass-full and
before cfail-full (because rfail comes before cfail). The order of tests
seems a little inconsistent, but reordering everywhere would obscure this
commit.

This allows you to distinguish between an option that defaulted, and an
option selected by the user

Optimization is now on by default. Closes #24405

libLTO fails to link here.

rust-installer never verifies.

Add a new test directory called 'rustdoc' where all files inside are documented
and run against the `htmldocck` script to have assertions about the output.

MacOS X does not ship with Java installed by default. Instead it
includes binary stubs that upon execution pop up a message suggesting
the installation of the JDK.

Since `javac` is only used when `antlr4` is available, it is possible
to work around the popup by only probing for `javac` if `antlr4` has
been successfully detected (in which case the JDK is probably already
installed on the system).

Fixes #23138.

This saves a bunch of a time and will make distributions smaller, as well as
avoiding filling the implementors page with internal garbage. Turn it back on
with `--enable-compiler-docs` if you want compiler docs during development.

Crates behind the facade are only documented on nightly/dev builds (where they
can be used).

[breaking-change]

Closes #23772
Closes #21297

The variable '$SHELL' is not actually defined by 'sh'.

LLVM older that 3.6 has a bug that cause assertions when compiling certain
constructs. For 3.5 there's still a chance that the bug might get fixed
in 3.5.2, so let's keep allowing to compile with it for it for now.

Not checking for 32/64 bit, since `uname -s` no longer contains an indicator (and `uname -m` returns correct results)

Using an extended regex fixes pattern matching on BSD sed.

Fixes #20467

When trying to build against a newer, local LLVM version it might be
preferable to have a flag to disable the LLVM version check instead of
having to modify the configure script.

Fixes #21998

the sed option `--in-place` (or `-i`) is a GNU extension, and it is not
portable to BSD system (openbsd and freebsd checked).

use an alternate construction in order to keep the semantic.