fix: update the VERSION variable assignment method

[vprashar2929]

This PR:

• fixes the issue the VERSION variable assignment
  from ?= to := to ensure immediate evaluation of $(GIT_VERSION)

• Use fetch_depth to fetch the tag info for computing the GIT_VERSION
  correctly while building Kepler images

• Removes the VERSION argument from the Dockerfile

• Removes the redundant bpftool COPY statement in build/Dockerfile

• Addresses issue Version incorrectly reported in the container images #1540

[github-actions]

🤖 SeineSailor

Here is a concise summary of the pull request changes:

Summary: This PR updates the VERSION variable assignment method, renames it to IMAGE_VERSION, and refactors Dockerfile configurations to ensure immediate evaluation and consistency.

Key Modifications:

1. Replaced ?= with := for immediate evaluation of $(GIT_VERSION).
2. Renamed VERSION to IMAGE_VERSION and added it back to image.yml for the release workflow.
3. Removed duplicate COPY statement from build/Dockerfile.
4. Updated LDFLAGS and build arguments to use IMAGE_VERSION instead of VERSION.
5. Added a conditional statement to the RUN make build command.

Impact: These changes fix issue #1540 and improve VERSION handling without affecting the external interface or behavior of the code. The signatures of exported functions and global data structures remain unaltered.

Observations: The changes are well-organized and address a specific issue. The use of := ensures immediate evaluation, which can prevent potential issues with variable assignment. The refactoring of Dockerfile configurations improves consistency and maintainability.

[sthaha]

@vprashar2929 , could you please explain why (instead of what) we are removing version?

[sthaha]

Lets make sure that this does not affect version in the release workflow.

[vprashar2929]

Kepler using the latest image:

kepler-latest-1  | I0620 06:22:45.350085  295372 gpu.go:42] Using dummy to obtain gpu power
kepler-latest-1  | I0620 06:22:45.351658  295372 exporter.go:100] Kepler running on version: v0.7.10-122-g9344179c
kepler-latest-1  | I0620 06:22:45.351682  295372 config.go:280] using gCgroup ID in the BPF program: false
kepler-latest-1  | I0620 06:22:45.351717  295372 config.go:282] kernel version: 6.8

Kepler using the dummy release image:

kepler-latest-1  | I0620 06:25:18.215265  298159 gpu.go:42] Using dummy to obtain gpu power
kepler-latest-1  | I0620 06:25:18.217287  298159 exporter.go:100] Kepler running on version: release-0.7.11
kepler-latest-1  | I0620 06:25:18.217362  298159 config.go:280] using gCgroup ID in the BPF program: false
kepler-latest-1  | I0620 06:25:18.217400  298159 config.go:282] kernel version: 6.8