fix: pin "which" dep at 2.21 & build h0b41bf4_1

[jimfangx]

tldr: the which package had a upstream update that included set -x and set -e in its conda activation script, which breaks the user terminal when the user performs . env.sh after rebuilding the conda lockfile and resetting up Chipyard.

when we regenerate the conda lock file using ${CY}/scripts/conda-lockfiles.sh (which is needed if sysroot_linux-64=2.28 version in ${CY}/conda-reqs/chipyard-base.yaml is higher than the glibc (ldd --version) version on the server CY is run on -- often needed on servers w/ eda tools) it bumps the which package which to version 2.23, which contains the following in the shell script [at ${CY}/.conda-env/etc/conda/activate.d] that is run during conda activation:

set -x
set -e
if [ "${SHELL}" = "/bin/bash" ]; then
    if [ "$(type -t which)" = "alias" ]; then
        unalias which
    elif [ "$(type -t which)" = "function" ]; then
        unset -f which
    fi
fi

the set -x and set -e gets sourced into the current terminal when we . env.sh and breaks the user terminal.

This PR pins the which dep in chipyard-extended.yaml to the version and build that exists in the current lockfile, so which doesn't get bumped when the lockfile is rebuilt.

Related PRs / Issues:

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

Contributor Checklist:

• Did you set main as the base branch?
• Is this PR's title suitable for inclusion in the changelog and have you added a changelog:<topic> label?
• Did you state the type-of-change/impact?
• Did you delete any extraneous prints/debugging code?
• Did you mark the PR with a changelog: label?
• (If applicable) Did you update the conda .conda-lock.yml file if you updated the conda requirements file?
• (If applicable) Did you add documentation for the feature?
• (If applicable) Did you add a test demonstrating the PR?

• (If applicable) Did you mark the PR as Please Backport?

CI Help:
Add the following labels to modify the CI for a set of features.
Generally, a label added only affect subsequent changes to the PR (i.e. new commits, force pushing, closing/reopening).
See ci:* for full list of labels:

• ci:fpga-deploy - Run FPGA-based E2E testing
• ci:local-fpga-buildbitstream-deploy - Build local FPGA bitstreams for platforms that are released
• ci:disable - Disable CI

changelog:fixed