fakecgo: add s390x support for CGO_ENABLED=0

[gdams]

What type of issue is this addressing?

feature

What this PR does | solves

Adds support for CGO_ENABLED=0 on s390x. Note that this will only work for Go 1.27+.

For those who want to test this you can easily do this via a docker container:

docker run --platform linux/s390x --rm \
  -v "$(pwd):/app" -w /app -e CGO_ENABLED=0 \
  golang:tip sh -lc '
    set -e
    mkdir -p /lib64
    ln -sf /usr/lib/s390x-linux-gnu/ld64.so.1 /lib64/ld64.so.1
    /usr/local/go/bin/go test .
  '

[hajimehoshi]

Interesting, but we cannot have tests right now, right?

[gdams]

Interesting, but we cannot have tests right now, right?

that's correct, the upstream fix only exists in master so we can test using the above docker command but unfortunely setup-go doesn't support gotip and manually running this would significantly slow down CI. I'd suggest that given that's unsupported until 1.27 you can just enable the testing at that point?

[hajimehoshi]

I suggest to hold this PR until Go 1.27 release candidate is released

[gdams]

I suggest to hold this PR until Go 1.27 release candidate is released

yup, I'm totally fine with this, I wanted to just get the assembly in a git repo somewhere so we didn't lose it :)