Modularize package detection

[jserv]

With the introduction of refined Kconfiglib, we can validate the package dependency via customized scripts, making configurations more flexible and accurate.

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Summary by cubic

Modularized build-time package detection with a new mk/deps.mk helper, replacing scattered pkg-config/sdl2-config calls. This unifies cflags/libs retrieval, supports multi-package inputs, and prepares for Kconfiglib-based dependency checks.

• Refactors
  • Added dep(flag-type, package[s]) in mk/deps.mk: try -config, then pkg-config; supports multiple packages; returns empty if not found; quiet by default, use V=1 for verbose.
  • Updated Makefile to use dep for pixman-1, libjpeg, libpng, sdl2, cairo, and neatvnc/aml/pixman-1, reducing repeated shell calls and centralizing dependency handling.

[cubic-dev-ai]

No issues found across 2 files