Change busybox to be musl linked

Dockerfile

@@ -1,3 +1,28 @@
+# We build our own busybox-static with musl, because the default
+# debian one links to glibc, and glibc implements rfc3484, and
+# "rule 9" of that rfc is grossly incompatible with kube headless
+# services.  We would like to start a discussion about all this
+# on the glibc mailing list, and for that we need nilcons-debian to
+# contain both glibc based (normal) and musl based (busybox) wget,
+# for demonstration purposes.
+#
+# Once this rfc3484 based glibc behaviour is fixed, we can remove this
+# hack and go back to using normal busybox-static from debian.
+FROM debian:bookworm AS busybox-build
+RUN </etc/apt/sources.list.d/debian.sources sed s/deb$/deb-src/ >/etc/apt/sources.list.d/debian-src.sources
+RUN apt-get update -q && apt-get install -y build-essential musl-tools && apt-get build-dep -y busybox
+RUN ln -s /usr/include/linux /usr/include/asm-generic /usr/include/*-gnu*/asm /usr/include/*-musl*
+RUN mkdir /tmp/bb && cd /tmp/bb \
+        && apt-get source busybox \
+        && mv /tmp/bb/busybox-* /tmp/bb/busybox \
+        && cd /tmp/bb/busybox \
+        && mkdir build-musl && cat debian/config/os/linux debian/config/pkg/static >build-musl/.config \
+        && sed -i s/CONFIG_EXTRA_COMPAT=y/CONFIG_EXTRA_COMPAT=n/ build-musl/.config \
+        && sed -i s/CONFIG_FEATURE_VI_REGEX_SEARCH=y/CONFIG_FEATURE_VI_REGEX_SEARCH=n/ build-musl/.config \
+        && sed -i s/CONFIG_UBIRENAME=y/CONFIG_UBIRENAME=n/ build-musl/.config \
+        && yes "" | make CC=musl-gcc LD=musl-gcc -C build-musl -f $PWD/Makefile KBUILD_SRC=$PWD oldconfig \
+        && make CC=musl-gcc LD=musl-gcc -C build-musl -f $PWD/Makefile KBUILD_SRC=$PWD
+
 FROM debian:bookworm
 RUN apt-get update -q \
         && apt-get install -y -q --no-install-recommends \
@@ -9,6 +34,8 @@ RUN apt-get update -q \
         && apt-get clean \
         && rm -rf /var/lib/apt/lists/*
 COPY bash-if-tty tini-if-1 /usr/bin/
+RUN dpkg-divert --rename --add /usr/bin/busybox
+COPY --from=busybox-build  /tmp/bb/busybox/build-musl/busybox /usr/bin/busybox
 ENTRYPOINT [ "/usr/bin/tini-if-1" ]
 CMD [ "/usr/bin/bash-if-tty" ]