Rollup merge of #152578 - heiher:ci-crosstool, r=Mark-Simulacrum

ci: Lock cross toolchain version and update docs

This PR locks the cross-toolchain component version to avoid unexpected changes when bumping crosstool-ng, and updates the toolchain configuration in the docs to match the actual setup.

try-job: dist-arm-linux-musl
try-job: dist-loongarch64-linux
try-job: dist-loongarch64-musl
try-job: dist-powerpc64-linux-musl
try-job: dist-powerpc64le-linux-gnu
try-job: dist-powerpc64le-linux-musl

Author: jhpratt