Rollup merge of #133801 - Gelbpunkt:powerpc64le-unknown-linux-musl-tier-2, r=jieyouxu,Urgau,Kobzol

Promote powerpc64le-unknown-linux-musl to tier 2 with host tools

MCP: https://github.com/rust-lang/compiler-team/issues/803

I'm using crosstool-ng for building a toolchain because GCC 9 from `musl-toolchain.sh` has float ABI issues (?) and can't compile LLVM, and writing a crosstool-ng config for a target feels less hacky than yet another target specific shell script. I also defined a kernel version, since there wasn't one specified before. If a lower version is desired, just let me know. I also tried to match the rust configure args with the loongarch64 musl tier 2 target.

The resulting compiler works fine, built with `DEPLOY=1 ./src/ci/docker/run.sh dist-powerpc64le-linux` and tested on Alpine Linux in a VM and on a bare metal POWER8 machine:
```
qemu-ppc64le:/tmp/rust-nightly-powerpc64le-unknown-linux-musl$ ash install.sh
install: creating uninstall script at /usr/local/lib/rustlib/uninstall.sh
install: installing component 'rustc'
install: installing component 'rust-std-powerpc64le-unknown-linux-musl'
install: installing component 'cargo'
install: installing component 'rustfmt-preview'
install: installing component 'rls-preview'
install: installing component 'rust-analyzer-preview'
install: installing component 'llvm-tools-preview'
install: installing component 'clippy-preview'
install: installing component 'miri-preview'
install: installing component 'rust-analysis-powerpc64le-unknown-linux-musl'
install: installing component 'llvm-bitcode-linker-preview'
install: WARNING: failed to run ldconfig. this may happen when not installing as root. run with --verbose to see the error

    rust installed.

qemu-ppc64le:~$ echo 'fn main() { println!("hello world"); }' > test.rs
qemu-ppc64le:~$ rustc test.rs
qemu-ppc64le:~$ ./test
hello world
qemu-ppc64le:~$ file test
test: ELF 64-bit LSB executable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), statically linked, BuildID[sha1]=596ee6abf9add487ebc54fb71c2076fb6faea013, with debug_info, not stripped
```

try-job: dist-powerpc64le-linux

3 files changed, 50 insertions, 1 deletions

diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index 2341d25ff09..1e9f5a33fc7 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -66,6 +66,7 @@
     - [powerpc-unknown-openbsd](platform-support/powerpc-unknown-openbsd.md)
     - [powerpc-unknown-linux-muslspe](platform-support/powerpc-unknown-linux-muslspe.md)
     - [powerpc64-ibm-aix](platform-support/aix.md)
+    - [powerpc64le-unknown-linux-musl](platform-support/powerpc64le-unknown-linux-musl.md)
     - [riscv32e*-unknown-none-elf](platform-support/riscv32e-unknown-none-elf.md)
     - [riscv32i*-unknown-none-elf](platform-support/riscv32-unknown-none-elf.md)
     - [riscv32im-risc0-zkvm-elf](platform-support/riscv32im-risc0-zkvm-elf.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index c4efe27efc2..db6612f9fff 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -97,6 +97,7 @@ target | notes
 `powerpc-unknown-linux-gnu` | PowerPC Linux (kernel 3.2, glibc 2.17)
 `powerpc64-unknown-linux-gnu` | PPC64 Linux (kernel 3.2, glibc 2.17)
 `powerpc64le-unknown-linux-gnu` | PPC64LE Linux (kernel 3.10, glibc 2.17)
+[`powerpc64le-unknown-linux-musl`](platform-support/powerpc64le-unknown-linux-musl.md) | PPC64LE Linux (kernel 4.19, musl 1.2.3)
 [`riscv64gc-unknown-linux-gnu`](platform-support/riscv64gc-unknown-linux-gnu.md) | RISC-V Linux (kernel 4.20, glibc 2.29)
 [`riscv64gc-unknown-linux-musl`](platform-support/riscv64gc-unknown-linux-musl.md) | RISC-V Linux (kernel 4.20, musl 1.2.3)
 [`s390x-unknown-linux-gnu`](platform-support/s390x-unknown-linux-gnu.md) | S390x Linux (kernel 3.2, glibc 2.17)
@@ -348,7 +349,6 @@ target | std | host | notes
 `powerpc-unknown-freebsd` | ? |   | PowerPC FreeBSD
 `powerpc64-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3
 [`powerpc64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
-`powerpc64le-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3, Little Endian
 [`powerpc64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/powerpc64
 [`powerpc64-ibm-aix`](platform-support/aix.md) | ? |  | 64-bit AIX (7.2 and newer)
 `riscv32gc-unknown-linux-gnu` | ✓ |   | RISC-V Linux (kernel 5.4, glibc 2.33)
diff --git a/src/doc/rustc/src/platform-support/powerpc64le-unknown-linux-musl.md b/src/doc/rustc/src/platform-support/powerpc64le-unknown-linux-musl.md
new file mode 100644
index 00000000000..3bd3f5d8b7f
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/powerpc64le-unknown-linux-musl.md
@@ -0,0 +1,48 @@
+# powerpc64le-unknown-linux-musl
+
+**Tier: 2**
+
+Target for 64-bit little endian PowerPC Linux programs using musl libc.
+
+## Target maintainers
+
+- [@Gelbpunkt](https://github.com/Gelbpunkt)
+- [@famfo](https://github.com/famfo)
+- [@neuschaefer](https://github.com/neuschaefer)
+
+## Requirements
+
+Building the target itself requires a 64-bit little endian PowerPC compiler that is supported by `cc-rs`.
+
+## Building the target
+
+The target can be built by enabling it for a `rustc` build.
+
+```toml
+[build]
+target = ["powerpc64le-unknown-linux-musl"]
+```
+
+Make sure your C compiler is included in `$PATH`, then add it to the `config.toml`:
+
+```toml
+[target.powerpc64le-unknown-linux-musl]
+cc = "powerpc64le-linux-musl-gcc"
+cxx = "powerpc64le-linux-musl-g++"
+ar = "powerpc64le-linux-musl-ar"
+linker = "powerpc64le-linux-musl-gcc"
+```
+
+## Building Rust programs
+
+This target are distributed through `rustup`, and otherwise require no
+special configuration.
+
+## Cross-compilation
+
+This target can be cross-compiled from any host.
+
+## Testing
+
+This target can be tested as normal with `x.py` on a 64-bit little endian
+PowerPC host or via QEMU emulation.