feat: aarch64 port - fix build system obstacles, add exception handling, page tables

scripts/check-arch-neutral.sh

@@ -93,8 +93,10 @@ if [ -n "$missing" ]; then
 fi
 echo "check-arch-neutral: $ARCH objects compile and every symbol resolves"
 
-if command -v "${KERNEL_LD:-ld.lld}" >/dev/null 2>&1; then
-    make ARCH="$ARCH" >/dev/null
+# Same lookup as kernel/GNUmakefile: a system ld.lld, else rustup's.
+lld="${KERNEL_LD:-$(command -v ld.lld || ls "$HOME"/.rustup/toolchains/*/lib/rustlib/*/bin/gcc-ld/ld.lld 2>/dev/null | head -n 1)}"
+if [ -n "$lld" ] && command -v "$lld" >/dev/null 2>&1; then
+    make ARCH="$ARCH" KERNEL_LD="$lld" >/dev/null
     echo "check-arch-neutral: linked kernel/bin-$ARCH/kernel"
 fi