Dockerfiles: Improve cross building.

[eiffel-fl]

Previously to this commit, it was possible to cross build the images from amd64 to arm64.
With this commit, cross building can now be done in any direction:

1. From amd64 to arm64.
2. From arm64 to amd64.

[eiffel-fl]

Before this commit, it was not possible to build ig-linux-amd64 from and arm64 computer:

francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ lscpu | head -1
Architecture:                    aarch64
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ git branch
  francis/cross-building
* main
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ make ig-linux-amd64
...
 => ERROR [builder 7/7] RUN  export CGO_ENABLED=1 ;  if [ "amd64" = 'arm64' ] ; then   export CC=aarch64-linux-gnu-gcc ;   export PKG_CONFIG_PATH=/usr/lib/aarch64-  10.4s
------
 > [builder 7/7] RUN    export CGO_ENABLED=1 ;  if [ "amd64" = 'arm64' ] ; then                 export CC=aarch64-linux-gnu-gcc ;               export PKG_CONFIG_PATH=/usr/lib/aarch64-linux-gnu/pkgconfig ;      fi ;    GOOS=linux GOARCH=amd64 go build                -ldflags "-X main.version=v0.19.0-19-gf34d53e8 -extldflags '-static'"     -o ig-linux-amd64                github.com/inspektor-gadget/inspektor-gadget/cmd/ig:
2.965 # runtime/cgo
2.965 gcc: error: unrecognized command-line option '-m64'
------
ERROR: failed to solve: executor failed running [/bin/sh -c export CGO_ENABLED=1 ;      if [ "${TARGETARCH}" = 'arm64' ] ; then                 export CC=aarch64-linux-gnu-gcc ;          export PKG_CONFIG_PATH=/usr/lib/aarch64-linux-gnu/pkgconfig ;   fi ;    GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build          -ldflags "-X main.version=${VERSION} -extldflags '-static'"                -o ig-${TARGETOS}-${TARGETARCH}                 github.com/inspektor-gadget/inspektor-gadget/cmd/ig]: exit code: 1
make: *** [Makefile:98: ig-linux-amd64] Error 1

It is now possible:

francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ git branch
* francis/cross-building
  main
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ lscpu | head -1
Architecture:                    aarch64
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ make ig-linux-amd64
...
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ file ig-linux-amd64 
ig-linux-amd64: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, BuildID[sha1]=bbeaf0544a48bff8f8d530a055258a3485113f31, for GNU/Linux 3.2.0, with debug_info, not stripped
francis-arm64-vm@francis-arm64-vmvm:~/inspektor-gadget$ exit
logout
Connection to IP closed.
$ sftp francis-arm64-vm@IP                                                            francis/test-scaling *% u=
Connected to IP.
sftp> get inspektor-gadget/ig-linux-amd64
Fetching /home/francis-arm64-vm/inspektor-gadget/ig-linux-amd64 to ig-linux-amd64
ig-linux-amd64                                                                                                                           100%   98MB  18.6MB/s   00:05    
sftp> bye
$ sudo ./ig-linux-amd64 trace exec --host                                                     francis/test-scaling *% u=
RUNTIME.CONTAINERNAME                                   PID        PPID       COMM             RET ARGS                                                                    
                                                        103102     91022      runc             0   /usr/bin/runc --root /var/run/docker/runtime-runc/moby --log /run/conta…
                                                        103111     103102     exe              0   /proc/self/exe init                                                     
wizardly_mclaren                                        103113     103102     sh               0   /bin/sh -c /etc/jupyter/docker_healthcheck.py || exit 1                 
wizardly_mclaren                                        103119     103113     docker_healthch  0   /etc/jupyter/docker_healthcheck.py                                      
wizardly_mclaren                                        103119     103113     python3          0   /opt/conda/bin/python3 /etc/jupyter/docker_healthcheck.py               

[burak-ok]

Looks good.

One comment is that ig-tests.Dockerfile also has a condition based on arm64. So maybe there we should also support arm64->amd64 compiling aswell to be aligned?

[eiffel-fl]

One comment is that ig-tests.Dockerfile also has a condition based on arm64. So maybe there we should also support arm64->amd64 compiling aswell to be aligned?

Good catch! I added the same logic there!

I will just check the result on AKS and ARO before merging.

[eiffel-fl]

Everything is green, let's merge it!
Thank you for the review!