remove redundant makefile-build workflow

Removed .github/workflows/makefile-build.yml as it duplicated
the functionality of the existing build.yml workflow.

The makefile-build workflow was added to demonstrate make build-all
but it created unnecessary duplication:

- build.yml: Builds on push/PR with matrix for parallel builds
- makefile-build.yml: Weekly + manual trigger using make build-all

The existing build.yml workflow already provides:
- Cross-platform builds for all supported platforms
- Artifact uploads for testing
- Triggered on every push/PR for immediate feedback

Users can run 'make build-all' locally if they want to build
all platforms in a single command.

Now we have a clean, focused workflow structure:
- ci.yml: Testing and verification
- build.yml: Cross-platform binary builds
- release.yml: Automated releases on tags

Co-authored-by: f0ssel <[email protected]>

Author: blink-so[bot]