-> `rustc --target armv7-none-eabi` will work

also build rust-std (rustup) components for them

-> `rustup target add armv7-none-eabi` will work

…D 13.0-CURRENT i386

rust-nightly has been failing to link since 2019-12-10 with variations of
```
 = note: ld: error: relocation R_386_PC32 cannot be used against symbol __rust_probestack; recompile with -fPIC
          >>> defined in /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libcompiler_builtins-6570a75fe85f0e1a.rlib(compiler_builtins-6570a75fe85f0e1a.compiler_builtins.2i519eqi-cgu.15.rcgu.o)
          >>> referenced by std.4xivr03c-cgu.14
          >>>               std-9bd70afd58e204b7.std.4xivr03c-cgu.14.rcgu.o:(_$LT$alloc..boxed..Box$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$A$GT$$GT$::call_once::h1c78ed6e734a2bfc (.llvm.10122419023709863394)) in archive /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libstd-9bd70afd58e204b7.rlib

          ld: error: relocation R_386_PC32 cannot be used against symbol __rust_probestack; recompile with -fPIC
          >>> defined in /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libcompiler_builtins-6570a75fe85f0e1a.rlib(compiler_builtins-6570a75fe85f0e1a.compiler_builtins.2i519eqi-cgu.15.rcgu.o)
          >>> referenced by std.4xivr03c-cgu.14
          >>>               std-9bd70afd58e204b7.std.4xivr03c-cgu.14.rcgu.o:(std::io::util::copy::h9115f048f2203467) in archive /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libstd-9bd70afd58e204b7.rlib
          clang-cpp: error: linker command failed with exit code 1 (use -v to see invocation)

error: aborting due to previous error

error: could not compile `rustc_macros`.
```
Full log: http://beefy17.nyi.freebsd.org/data/head-i386-default/p523508_s356869/logs/rust-nightly-1.42.0.20200118.log

AFAICT it stopped building after bumping compiler_builtins to 0.1.22
in rust-lang#67110.

it needs some upstream changes in the build script of the compiler-builtins
crate

…crichton

add bare metal ARM Cortex-A targets to rustc

-> `rustc --target armv7a-none-eabi` will work

also build rust-std (rustup) components for them

-> `rustup target add armv7a-none-eabi` will work

this completes our bare-metal support of ARMv7 cores on stable Rust (by 1.42 or 1.43)

(these target specifications have been tested on a real (no emulation / QEMU) [Cortex-A7 core](https://github.com/iqlusioninc/usbarmory.rs/))

…ichton

Unbreak linking with lld 9 on FreeBSD 13.0-CURRENT i386

Add -Wl,-znotext to default linker flags to link with lld 9 on FreeBSD 13.0-CURRENT i386 where rust-nightly has been failing to link since 2019-12-10 with variations of
```
 = note: ld: error: relocation R_386_PC32 cannot be used against symbol __rust_probestack; recompile with -fPIC
          >>> defined in /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libcompiler_builtins-6570a75fe85f0e1a.rlib(compiler_builtins-6570a75fe85f0e1a.compiler_builtins.2i519eqi-cgu.15.rcgu.o)
          >>> referenced by std.4xivr03c-cgu.14
          >>>               std-9bd70afd58e204b7.std.4xivr03c-cgu.14.rcgu.o:(_$LT$alloc..boxed..Box$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$A$GT$$GT$::call_once::h1c78ed6e734a2bfc (.llvm.10122419023709863394)) in archive /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libstd-9bd70afd58e204b7.rlib

          ld: error: relocation R_386_PC32 cannot be used against symbol __rust_probestack; recompile with -fPIC
          >>> defined in /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libcompiler_builtins-6570a75fe85f0e1a.rlib(compiler_builtins-6570a75fe85f0e1a.compiler_builtins.2i519eqi-cgu.15.rcgu.o)
          >>> referenced by std.4xivr03c-cgu.14
          >>>               std-9bd70afd58e204b7.std.4xivr03c-cgu.14.rcgu.o:(std::io::util::copy::h9115f048f2203467) in archive /wrkdirs/usr/ports/lang/rust-nightly/work/rustc-nightly-src/build/i686-unknown-freebsd/stage1/lib/rustlib/i686-unknown-freebsd/lib/libstd-9bd70afd58e204b7.rlib
          clang-cpp: error: linker command failed with exit code 1 (use -v to see invocation)

error: aborting due to previous error

error: could not compile `rustc_macros`.
```
Full log: http://beefy17.nyi.freebsd.org/data/head-i386-default/p523508_s356869/logs/rust-nightly-1.42.0.20200118.log

AFAICT it stopped building after bumping compiler_builtins to 0.1.22 in rust-lang#67110.

…chton

Update cargo, books

## cargo

9 commits in ad3dbe10e1e654fb1f032a5dd9481d7cbaa00d65..f6449ba236db31995255ac5e4cad4ab88296a7c6
2020-01-13 21:37:15 +0000 to 2020-01-21 16:15:39 +0000
- Fix wrong directories in host_libdir. (rust-lang/cargo#7798)
- Update humantime requirement from 1.2.0 to 2.0.0 (rust-lang/cargo#7815)
- Fix doc_target test which no longer works on stable/beta. (rust-lang/cargo#7817)
- Fix some erroneous em-dashes in man pages. (rust-lang/cargo#7814)
- fix some clippy warnings (rust-lang/cargo#7808)
- Don't assume iowait always increases on Linux (rust-lang/cargo#7803)
- Add and update some doc comments. (rust-lang/cargo#7800)
- Consistently use em-dash in environment documentation page. (rust-lang/cargo#7799)
- Load credentials only when needed (rust-lang/cargo#7774)

## reference

3 commits in e115753..11e893f
2019-12-22 13:13:14 +0100 to 2020-01-18 21:24:08 +0100
- Small improvements to types/pointer.md (rust-lang/reference#726)
- repr(transparent): mention align=1 requirement (rust-lang/reference#737)
- Elaborate on how to use an extern static correctly (rust-lang/reference#736)

## book

4 commits in 5c5cfd2e94cd42632798d9bd3d1116133e128ac9..87dd6843678575f8dda962f239d14ef4be14b352
2019-12-16 09:27:21 -0600 to 2020-01-20 15:20:40 -0500
- Fix listing numbers (rust-lang/book#2227)
- Move `async` and `await` keywords to 'Currently in Use' (rust-lang/book#2140)
- More cleanup - remove unneeded files (rust-lang/book#2213)
- Small cleanups extracted from the bigger pr i'm working on (rust-lang/book#2212)

## rust-by-example

1 commits in 1d59403cb5269c190cc52a95584ecc280345495a..1c2bd024d13f8011307e13386cf1fea2180352b5
2019-12-27 08:27:05 -0300 to 2020-01-20 12:18:36 -0300
- CamelCase -> UpperCamelCase (rust-lang/rust-by-example#1302)

## embedded-book

1 commits in 9493b7d4dc97eda439bd8780f05ad7b234cd1cd7..4d78994915af1bde9a95c04a8c27d8dca066232a
2019-12-27 20:05:00 +0000 to 2020-01-14 08:25:25 +0000
- Update .gitattributes  (rust-embedded/book#221)

typeck: simplify the handling of `diverges`

Some drive-by cleanup while working on `hir::ExprKind::Let`.
Ostensibly, this has some perf benefits due to reduced allocation and whatnot as well.

r? @eddyb