jail: Use the right arch for a pkgbase jail

[jlduran]

This is currently a problem for anything not amd64 when building pkgbase jails. Strip the ARCH and use only what corresponds to TARGET_ARCH.

[jlduran]

Test plan:

# poudriere jail -c -j generic-15 -m pkgbase=base_latest -U https://pkg.freebsd.org -v 15 -K generic
# poudriere jail -l
JAILNAME    VERSION         OSVERSION ARCH          METHOD  TIMESTAMP           PATH
generic-15  15.0-CURRENT              arm64.aarch64 pkgbase 2024-10-15 16:27:01 /usr/local/poudriere/jails/generic-15

[jlduran]

cc/ @emaste

[jlduran]

Note

The OSVERSION does not show up because there is no /sys in the jail (not related to this change).

EDIT: A workaround/fix is offered in a separate commit.

[bdrewery]

I don't use pkgbase or touch image ever, so need a review from someone else to get this in.

[jlduran]

Rebase.

Let's wait for @bapt or @manu then. Thank you!

I'll take the rebase as an opportunity to explain the reasoning behind the changes.

This pull request contains two commits:

1. get_host_arch() sets ARCH as $(uname -m).$(uname -p), if both are the same (as is the case for amd64), then it just uses one. For all the other architectures, both values will differ. pkg ABI uses FreeBSD:<version>:$(uname -p), so we must trim the uname -m part.

2. On some installations, make distributeworld may have not been executed (as is the case for pkgbase). Among other things, it installs the symlink /sys ->/usr/src/sys (https://github.com/freebsd/freebsd-src/blob/c3f8900e696998c410dc16f9bd9d45c24c413e6b/Makefile.inc1#L1522). Arguably, this symlink can be added to the pkgbase as a post-install scrpt.