There's a merged pull request on the void-packages repository

xbps-src/shutils/cross.sh: error out if cross toolchain can't be compiled
https://github.com/void-linux/void-packages/pull/16086

Description:
$rval was the return code of pkg_available and not of build.sh, since
pkg_available returns 0. because of this install_cross_pkg() would
always return 0 for success.

Can be easily tested by running something like `./xbps-src -m masterdir-musl pkg dash -a aarch64` before and afterwards.