ci: expand build.yml to 4-arch matrix (amd64, arm64, armhf, riscv64)

[rkt0209]

Overview

This pull request establishes a production-grade, multi-architecture CI/CD pipeline for libppd using GitHub Actions. It standardizes our testing infrastructure by migrating from a single-architecture build to a comprehensive 4-architecture matrix matching the modern OpenPrinting workflow standard.

Changes

• Multi-Arch Test Matrix: Integrated a QEMU-emulated build and test matrix supporting four architectures: amd64, arm64, riscv64, and armhf.
• Automated Test Execution: Configured the pipeline to execute make check V=1 VERBOSE=1 across all target architectures, ensuring full validation of our modular C unit test suites on every commit.
• Static Analysis Integration: Embedded automated cppcheck and GitHub CodeQL analysis routines on the native amd64 runner to proactively intercept memory safety vulnerabilities, undefined behaviors, and regressions.
• Artifact Management: Added automated uploading of test-suite.log on build or test failures to streamline remote debugging of emulated architecture edge cases.

Testing Surface Covered

The pipeline successfully provisions all required upstream and downstream dependencies (cups, libcupsfilters, qpdf, ghostscript, poppler, etc.) before configuring the build tree and verifying standard exit statuses.