fix(arm64): resolve dual-glibc loading that triggers stack-canary aborts

Second nft crash report from QEMU virt:

  failed to set up pod masquerade
    nft add table ip kubesolo-masq:
      signal: aborted (output: *** stack smashing detected ***: terminated)

Root cause: two glibcs are visible to dynamically-linked binaries in the
rootfs. piCore64 ships glibc at /lib/libc.so.6; we copy the build host's
glibc (for the iptables-nft / nft / xtables-modules family) to
/lib/$LIB_ARCH/libc.so.6. The dynamic linker can resolve one binary's
NEEDED libc.so.6 to piCore's and another (via transitive load through
e.g. libnftables.so.1) to ours. Each libc has its own __stack_chk_guard
global; stack frames whose canary was written by code from libc-A and
checked by code from libc-B trip "stack smashing detected" → SIGABRT.
This didn't fire before nft was added because no host-installed dyn
binary actually got invoked before kubesolo crashed at first-boot
preflight.

Three layered fixes in inject-kubesolo.sh:

1. Bundle the full glibc family (was just libc.so.6 + ld). Now also
   libpthread, libdl, libm, libresolv, librt, libanl, libgcc_s. Without
   these, transitively-loaded host libs could pull them in from piCore's
   /lib and re-introduce the split.

2. After bundling, delete piCore's duplicates from /lib/ where our copy
   exists in /lib/$LIB_ARCH/. The dynamic linker's search now has
   exactly one match per soname.

3. Write /etc/ld.so.conf giving /lib/$LIB_ARCH precedence over /lib, and
   run `ldconfig -r "$ROOTFS"` to bake an explicit /etc/ld.so.cache.
   The runtime linker uses the cache (when present) instead of falling
   back to compiled-in default paths, making lookup order deterministic.

Also done (followups from previous commit):

- build/Dockerfile.builder gains nftables so docker-build picks up nft.
- .gitea/workflows/release.yaml's amd64 build job installs iptables +
  nftables (previously only listed iptables-related libs but not the
  CLIs themselves).

Verified by shellcheck. End-to-end QEMU verification on the Odroid next.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

build/Dockerfile.builder

@@ -30,6 +30,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libarchive-tools \
     libelf-dev \
     libssl-dev \
+    nftables \
     make \
     parted \
     squashfs-tools \