set -u in a build script silently breaks eval of a user's setup command

If a script runs under set -u and evaluates a user-supplied environment setup command in a subshell, e.g. d=$( (eval "$SETUP" >/dev/null 2>&1; echo "$TOOL_HOME") ), any unset variable the setup references (very common in site setup scripts: export LD_LIBRARY_PATH=$X/lib:$LD_LIBRARY_PATH) aborts the subshell before the echo. With stderr redirected you get an empty result and a misleading 'tool not found'. Verified with both /bin/sh and bash on macOS: output is empty, not 'after'. Fix: ( set +u; eval "$SETUP" </dev/null ...). Also add </dev/null whenever the script itself arrives on stdin (bash -s), or a setup that reads stdin swallows the rest of the script.