build-redbear.sh: enable dep-level parallel cooking by default

Export COOKBOOK_COOK_JOBS (default JOBS/4, min 1) so the full build cooks
independent same-level recipes concurrently. Override with COOKBOOK_COOK_JOBS=1
for serial. See the cook orchestrator's run_parallel_cook.

local/scripts/build-redbear.sh

@@ -9,7 +9,7 @@ PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
 # REDBEAR_VERSION (which tracks the OS release derived from the git branch).
 # Starts at 1.0 and is bumped AUTOMATICALLY on every change by the pre-commit
 # git hook (local/scripts/bump-build-version.sh); do not edit the minor by hand.
-BUILD_REDBEAR_VERSION="1.8"
+BUILD_REDBEAR_VERSION="1.9"
 
 # ── Colorized output ──────────────────────────────────
 # Enabled only on a TTY with NO_COLOR unset, so redirected build logs and CI
@@ -301,6 +301,12 @@ fi
 # gates and the sub-scripts observe the flag-provided values.
 CONFIG="redbear-full"
 JOBS="${JOBS:-$(nproc)}"
+# Dep-level parallel recipe cooking: cook this many independent (same-level)
+# recipes at once. The make-job budget (JOBS) is divided across the concurrent
+# cooks per level, so lone heavyweight recipes still get the full -j. Default to
+# a quarter of JOBS (min 1); override with COOKBOOK_COOK_JOBS=1 to force serial.
+COOK_JOBS_DEFAULT=$(( JOBS / 4 )); [ "$COOK_JOBS_DEFAULT" -lt 1 ] && COOK_JOBS_DEFAULT=1
+export COOKBOOK_COOK_JOBS="${COOKBOOK_COOK_JOBS:-$COOK_JOBS_DEFAULT}"
 APPLY_PATCHES="${APPLY_PATCHES:-1}"
 NO_CACHE=0
 CHECK_SWEEP=0