New issue by pullmoll on void-packages repository

https://github.com/void-linux/void-packages/issues/26867

Description:
I saw this happening now several times when running builds for #26811 :
When cross compiling packages on a branch and a host packages is missing, it is (sometimes?) created in the `binpkgs` instead of the `binpkgs/${_gitbranch}` path.

I have not yet tracked down where this comes from and whether it happens only occasionally or always, yet it seems the "$XBPS_REPOSITORY" environment is reset to the default w/o respecting the "$XBPS_ALT_REPOSITORY" value. Or perhaps the `$XBPS_ALT_REPOSITORY` value is unset and lost for a host dependency build.