rebuild-cascade: walk [build].dependencies and [build].dev_dependencies

Previously the script only parsed [package].dependencies, missing
the build-time-only consumers that the cookbook's
get_build_deps_recursive() picks up via [build].{dependencies,
dev_dependencies}. This caused 'rebuild-cascade.sh relibc' to report
'nothing to do' even though the cookbook correctly identifies
uutils, libpciaccess, relibc-tests, and other packages as relibc
build-dep consumers and rebuilds them under 'make live'.

The fix is to also walk the [build] section. The cookbook's own
parser uses the same convention.

local/scripts/rebuild-cascade.sh

@@ -79,24 +79,35 @@ extract_recipe_deps() {
         return
     fi
 
-    # Multi-line dependencies = [ ... ] extraction. Handles `]` on its own line.
+    # Both [package] and [build] sections contribute deps. The cookbook's
+    # get_build_deps_recursive() walks both; this script must match.
+    local in_section=""
     local in_deps=0
     while IFS= read -r line; do
+        if [[ "${line}" =~ ^[[:space:]]*\[([^]]+)\][[:space:]]*$ ]]; then
+            local sect="${BASH_REMATCH[1]// /}"
+            if [ "${sect}" = "package" ] || [ "${sect}" = "build" ]; then
+                in_section="${sect}"
+            else
+                in_section=""
+            fi
+            in_deps=0
+            continue
+        fi
+        [ -z "${in_section}" ] && continue
+
         if [ "${in_deps}" = 1 ]; then
-            # Strip whitespace, quotes, trailing commas
             local item="${line}"
             item="${item## }"; item="${item%% }"
             item="${item#\"}"; item="${item%\"}"
             item="${item%,}"
             [ -n "${item}" ] && deps+="${item},"
-            # Section closes on a line that is just `]` or contains `]`
             if [[ "${line}" =~ ^[[:space:]]*\] ]]; then
                 in_deps=0
             fi
             continue
         fi
-        # Check if this line starts `dependencies = [`
-        if [[ "${line}" =~ ^[[:space:]]*dependencies[[:space:]]*=[[:space:]]*\[ ]]; then
+        if [[ "${line}" =~ ^[[:space:]]*(dependencies|dev_dependencies)[[:space:]]*=[[:space:]]*\[ ]]; then
             in_deps=1
             local inline="${line#*=}"
             inline="${inline#[}"