Added QEMU support to cross build s390x image

[guirish]

Added QEMU support to cross build s390x image

[CLAassistant]

All committers have signed the CLA.

[huoqifeng]

@guirish thanks for raising the PR.
@caseydavenport may you help review this? I can confirm cross-platform build works well for s390x on a amd64 ubuntu 20.04 box, I tried it, here is the logs:

root@geodesic1:~/go/src/github.com/projectcalico/bpftool# uname -a
Linux xxx 5.4.0-109-generic #123-Ubuntu SMP Fri Apr 8 09:10:54 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
root@geodesic1:~/go/src/github.com/projectcalico/bpftool# pwd
/root/go/src/github.com/projectcalico/bpftool
root@geodesic1:~/go/src/github.com/projectcalico/bpftool# ARCH=s390x make image
# Make sure we re-pull the base image to pick up security fixes.
# Limit the build to use only one CPU, This helps to work around qemu bugs such as https://bugs.launchpad.net/qemu/+bug/1098729
docker build  --build-arg KERNEL_REF=v5.3 --build-arg KERNEL_REPO=git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git --cpuset-cpus 0 --pull -t calico/bpftool:v5.3-s390x -f Dockerfile.s390x .
Sending build context to Docker daemon  148.5kB
Step 1/14 : FROM alpine:3.11 as qemu
3.11: Pulling from library/alpine
Digest: sha256:bcae378eacedab83da66079d9366c8f5df542d7ed9ab23bf487e3e1a8481375d
Status: Image is up to date for alpine:3.11
 ---> a787cb986503
Step 2/14 : ARG QEMU_VERSION=6.1.0-8
 ---> Using cache
 ---> 112bb4822efc
Step 3/14 : ARG QEMU_ARCHS="s390x"
 ---> Using cache
 ---> f82b0a2c34b1
Step 4/14 : RUN apk --update add curl
 ---> Using cache
 ---> 16312a59055c
Step 5/14 : RUN curl -L https://github.com/multiarch/qemu-user-static/releases/download/v${QEMU_VERSION}/qemu-${QEMU_ARCHS}-static.tar.gz | tar zxvf - -C /usr/bin &&    chmod +x /usr/bin/qemu-s390x-static
 ---> Using cache
 ---> e3745cb24673
Step 6/14 : FROM s390x/debian:buster-slim as bpftool-build
buster-slim: Pulling from s390x/debian
Digest: sha256:4686d70ade80f2a41465e1b860e35ecf8eeaf2c3ac70c773dc03a21978c85d92
Status: Image is up to date for s390x/debian:buster-slim
 ---> 3b649080a399
Step 7/14 : ARG KERNEL_REPO=git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
 ---> Using cache
 ---> 3da36d50cba2
Step 8/14 : ARG KERNEL_REF=master
 ---> Using cache
 ---> 7ef015135ab4
Step 9/14 : COPY --from=qemu /usr/bin/qemu-s390x-static /usr/bin/
 ---> Using cache
 ---> 7f4d595ac3a9
Step 10/14 : RUN apt-get update && apt-get upgrade -y && apt-get install -y --no-install-recommends     gpg gpg-agent libelf-dev libmnl-dev libc-dev iptables libgcc-8-dev     bash-completion binutils binutils-dev make git curl     ca-certificates xz-utils gcc pkg-config bison flex build-essential && apt-get purge --auto-remove && apt-get clean
 ---> Using cache
 ---> 2cfdd0455777
Step 11/14 : WORKDIR /tmp
 ---> Using cache
 ---> a18cf3e8bb42
Step 12/14 : RUN git clone --depth 1 -b $KERNEL_REF $KERNEL_REPO && cd linux/tools/bpf/bpftool/ && sed -i '/CFLAGS += -O2/a CFLAGS += -static' Makefile && sed -i 's/LIBS = -lelf $(LIBBPF)/LIBS = -lelf -lz $(LIBBPF)/g' Makefile && printf 'feature-libbfd=0\nfeature-libelf=1\nfeature-bpf=1\nfeature-libelf-mmap=1' >> FEATURES_DUMP.bpftool && FEATURES_DUMP=`pwd`/FEATURES_DUMP.bpftool make -j `getconf _NPROCESSORS_ONLN` && strip bpftool && ldd bpftool 2>&1 | grep -q -e "Not a valid dynamic program" 	-e "not a dynamic executable" || 	( echo "Error: bpftool is not statically linked"; false ) && mv bpftool /usr/bin && rm -rf /tmp/linux
 ---> Using cache
 ---> cf0fe9f0331f
Step 13/14 : FROM scratch
 --->
Step 14/14 : COPY --from=bpftool-build /usr/bin/bpftool /bpftool
 ---> Using cache
 ---> 7ae0c91c5d59
Successfully built 7ae0c91c5d59
Successfully tagged calico/bpftool:v5.3-s390x

I think we'll need build images following in order: bpftool -> go-build -> calico.
The PRs in other project will be changed accordingly.