ci: define runas function inline

We don't have `test/units/util.sh`, which provides the definition of `runas` function in the RHEL9 codebase

Also partially backport systemd/systemd@c7bf195

rhel-only

Related: RHEL-35703

test/test-functions

@@ -206,6 +206,7 @@ BASICTOOLS=(
     seq
     setfattr
     setfont
+    setpriv
     setsid
     sfdisk
     sh
@@ -2616,10 +2617,10 @@ inst_binary() {
     # Same as above, but we need to wrap certain libraries unconditionally
     #
     # chown, getent, login, su, useradd, userdel - dlopen()s (not only) systemd's PAM modules
-    # ls, stat - pulls in nss_systemd with certain options (like ls -l) when
+    # ls, setpriv, stat - pulls in nss_systemd with certain options (like ls -l) when
     #            nsswitch.conf uses [SUCCESS=merge] (like on Arch Linux)
     # tar - called by machinectl in TEST-25
-    if get_bool "$IS_BUILT_WITH_ASAN" && [[ "$bin" =~ /(chown|getent|login|id|ls|stat|su|tar|useradd|userdel)$ ]]; then
+    if get_bool "$IS_BUILT_WITH_ASAN" && [[ "$bin" =~ /(chown|getent|login|id|ls|setpriv|stat|su|tar|useradd|userdel)$ ]]; then
         wrap_binary=1
     fi
 

test/units/testsuite-65.sh

@@ -6,6 +6,13 @@ set -eux
 # shellcheck source=test/units/assert.sh
 . "$(dirname "$0")"/assert.sh
 
+# On RHEL9 we don't have the `util.sh` script, so we need to define the `runas` function here
+runas() {
+    local userid="${1:?}"
+    shift
+    XDG_RUNTIME_DIR=/run/user/"$(id -u "$userid")" setpriv --reuid="$userid" --init-groups "$@"
+}
+
 systemctl log-level debug
 export SYSTEMD_LOG_LEVEL=debug