Enables multi architecture builds for dns_interceptor

[Ghost-B0t]

What this PR does / why we need it:
Enables multi-architecture builds for "dns_interceptor" binary to support ARM64 based chaos. Earlier it only built for AMD64.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #697

Special notes for your reviewer:

[xnaveenx]

Hi @Ghost-B0t, thanks for working on this!

I am not a maintainer, but I wanted to help verify this fix on my local Apple Silicon (M2) setup.

Observation:
The build failed locally for me. I dug a little deeper and noticed that main.go in custom/dns_interceptor seems to have hardcoded CGO flags pointing to x86_64 paths:

#cgo LDFLAGS: -L/usr/lib64/ -L/usr/lib/x86_64-linux-gnu/ -ldl

Result: Because of this, running GOOS=linux GOARCH=arm64 go build seems to trigger a build constraint error on ARM architectures.

Could you please double-check if we need to update those flags to support the multi-arch build? I'd be happy to test again once update!

[Jonsy13]

Hi @Ghost-B0t, thanks for working on this!

I am not a maintainer, but I wanted to help verify this fix on my local Apple Silicon (M2) setup.

Observation: The build failed locally for me. I dug a little deeper and noticed that main.go in custom/dns_interceptor seems to have hardcoded CGO flags pointing to x86_64 paths:

#cgo LDFLAGS: -L/usr/lib64/ -L/usr/lib/x86_64-linux-gnu/ -ldl

Result: Because of this, running GOOS=linux GOARCH=arm64 go build seems to trigger a build constraint error on ARM architectures.

Could you please double-check if we need to update those flags to support the multi-arch build? I'd be happy to test again once update!

Correct, @Ghost-B0t You may want to try by updating the flag to

#cgo LDFLAGS: -ldl

[Ghost-B0t]

Hey @xnaveenx @Jonsy13 Thanks for the reviews. I have updated the flag to remove architecture dependency and CGO was disabled for any builds, I have parameterized it, keeping the default as disabled as dns_interceptor needs CGo.
Please let me know if there are any other suggestions on the same.

[xnaveenx]

I verified this using a Dockerized Linux environment on Apple Silicon to ensure a clean cross-compile.

Status: Verified
Ran the following build command inside a golang:1.23 container:
CGO_ENABLED=1 GOOS=linux GOARCH=64 go build -v -o dns_interceptor_linux_arm64 .

Result:
The build passed, and the output binary is correct:
ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1

The fix looks solid on my end. Looking forward to seeing this merged! Thanks again @Ghost-B0t

[Ghost-B0t]

@Jonsy13 Any updates on this?