fix: bits_pthread cbindgen needs stddef.h for size_t type

The generated bits/pthread.h uses size_t but had no includes.
Also added openat cache vars to m4 recipe for gnulib cross-compilation.

scripts/build-iso.sh

@@ -11,6 +11,8 @@ esac
 CONFIG_NAME="redbear-mini"
 ARCH="x86_64"
 ALLOW_UPSTREAM=0
+NO_CACHE=0
+DISTCLEAN=0
 
 usage() {
     cat <<EOF
@@ -19,8 +21,12 @@ Usage: $(basename "$0") [OPTIONS] [CONFIG_NAME] [ARCH]
 Build a Red Bear OS live ISO for real bare metal.
 
 Options:
-  --upstream          Allow Redox/upstream recipe source refresh during build
-  -h, --help          Show this help
+  --upstream             Allow Redox/upstream recipe source refresh during build
+  --no-cache             Rebuild from scratch, discarding recipe build caches and
+                         package repository (preserves cross-compiler toolchain)
+  --no-cache-distclean   Full rebuild including cross-compiler toolchain
+                         (use when toolchain itself is broken or outdated)
+  -h, --help             Show this help
 
 Supported targets:
   redbear-full        Full desktop ISO (Wayland + KDE + GPU drivers)
@@ -39,6 +45,12 @@ while [ $# -gt 0 ]; do
         --upstream)
             ALLOW_UPSTREAM=1
             ;;
+        --no-cache)
+            NO_CACHE=1
+            ;;
+        --no-cache-distclean)
+            DISTCLEAN=1
+            ;;
         -h|--help)
             usage
             exit 0
@@ -86,6 +98,16 @@ fi
 echo "Building Red Bear OS ISO for real bare metal"
 echo "  config: ${CONFIG_NAME}"
 echo "  arch:   ${ARCH}"
+if [ "$DISTCLEAN" -eq 1 ]; then
+    echo "  cache:   full distclean (rebuilding toolchain + packages)"
+    make clean
+elif [ "$NO_CACHE" -eq 1 ]; then
+    echo "  cache:   disabled (rebuilding packages, preserving toolchain)"
+    make repo_clean
+    rm -rf repo
+    # Also clean local recipe targets that repo_clean misses
+    find local/recipes -maxdepth 4 -name "target" -type d -exec rm -rf {} + 2>/dev/null || true
+fi
 if [ "$ALLOW_UPSTREAM" -eq 1 ]; then
     echo "  upstream recipe refresh: enabled"
     REPO_OFFLINE=0 COOKBOOK_OFFLINE=false make live CONFIG_NAME="${CONFIG_NAME}" ARCH="${ARCH}"