Transition to Cross-Compilation for faster Docker Build Times

[dlaw4608]

closes #787

This pull request introduces significant improvements to the Docker build process by implementing cross-compilation.

Building arm64 image via QEMU takes over 15 mins on github actions, making it slow to build for development.

Building the image via cross compile dropped this build time to 2 min 30

Changes Made

1. Dockerfile Updates:

   • Introduced cross-compilation support by using ARG TARGETARCH.
   • Utilized --platform=$BUILDPLATFORM for multi-platform builds with Docker Buildx.

2. Workflow File:

   • Updated the workflow to leverage Docker Buildx for building and pushing images to multiple platforms (linux/amd64, linux/arm64).
   • Removed reliance on QEMU emulation, significantly speeding up the build process.

Benefits

• Faster Build Times: The new build process reduces the time from approximately 16 minutes to just 2 minutes and 30 seconds, representing an almost 8x improvement.
• Optimised Build Efficiency: Reduces overhead and simplifies the build process by eliminating the need for emulation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.89%. Comparing base (ece13e8) to head (96b0fcc).
Report is 163 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #790      +/-   ##
==========================================
+ Coverage   80.20%   81.89%   +1.68%     
==========================================
  Files          64       76      +12     
  Lines        4492     6114    +1622     
==========================================
+ Hits         3603     5007    +1404     
- Misses        600      755     +155     
- Partials      289      352      +63     

Flag	Coverage Δ
bare-k8s-integration	4.48% <0.00%> (?)
controllers-integration	71.73% <100.00%> (?)
gatewayapi-integration	10.99% <0.00%> (?)
integration	?
istio-integration	56.11% <0.00%> (?)
unit	31.45% <0.00%> (+1.42%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
api/v1beta1 (u)	71.42% <55.55%> (ø)
api/v1beta2 (u)	85.35% <80.00%> (-6.08%)	⬇️
pkg/common (u)	88.13% <ø> (-0.70%)	⬇️
pkg/istio (u)	72.50% <ø> (-1.41%)	⬇️
pkg/log (u)	94.73% <ø> (ø)
pkg/reconcilers (u)	∅ <ø> (∅)
pkg/rlptools (u)	83.64% <ø> (+4.19%)	⬆️
controllers (i)	82.22% <83.91%> (+5.42%)	⬆️

Files	Coverage Δ
controllers/dnspolicy_status.go	82.02% <100.00%> (-4.35%)	⬇️

... and 42 files with indirect coverage changes

[KevFan]

Rebase issue? I dont think this file and the files changes in tests/common/dnspolicy should be part of this PR 🤔

[dlaw4608]

Ah I must have squashed @makslion's commit into my own, will fix.