ci(installer-iso): /tmp not /var for livemedia resultdir

/var/lmc-out-PID kept being marked 'exists' by livemedia even after
rm -rf. Probably bind-mount or tmpfs from runner persists /var.
Switch to /tmp/lmc-out-PID — act job container's /tmp is fresh per
run.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/build-installer-iso.yml

@@ -62,25 +62,26 @@ jobs:
       - name: Build installer ISO with livemedia-creator
         run: |
           set -euxo pipefail
-          # livemedia-creator refuses an existing resultdir of any kind
-          # (even empty + just-mkdir'd). Force-clean + use a fresh path
-          # outside the workspace; copy artefacts back at the end.
-          OUT=/var/lmc-out-$$
-          rm -rf "$OUT" /var/lmc
-          mkdir -p /var/lmc
+          # livemedia-creator refuses ANY pre-existing resultdir, even
+          # one we just rm'd — somewhere in /var the path is recreated.
+          # Use /tmp (act-job-container fresh tmpfs) + unique suffix.
+          OUT="/tmp/lmc-out-$$"
+          TMPD="/tmp/lmc-$$"
+          rm -rf "$OUT" "$TMPD"
+          mkdir -p "$TMPD"
           ln -sfn "$GITHUB_WORKSPACE" /work
+          ls -ld "$OUT" 2>&1 || echo "[OK] $OUT does not exist (expected)"
           livemedia-creator \
             --make-iso \
             --no-virt \
             --ks kickstart/install-ostreecontainer-installer.ks \
             --resultdir "$OUT" \
-            --tmp /var/lmc \
+            --tmp "$TMPD" \
             --volid "veilor-os-installer-${RELEASEVER}" \
             --project "veilor-os" \
             --releasever "$RELEASEVER" \
             --logfile "$OUT/build.log" \
             2>&1 | tee /tmp/build.log
-          # Move artefacts back into workspace for downstream steps.
           mkdir -p build/out
           cp -a "$OUT"/. build/out/
           cp -a /tmp/build.log build/out/build.log 2>/dev/null || true