Use pkg-config to find libraries

guix.scm

@@ -10,6 +10,7 @@
 (use-modules
  (gnu packages audio)
  (gnu packages gl)
+ (gnu packages pkg-config)
  (gnu packages sdl)
  (gnu packages video)
  (guix build-system cmake)
@@ -38,6 +39,8 @@
      (list #:tests? #f))
     (inputs
      (list ffmpeg mesa openal sdl2))
+    (native-inputs
+     (list pkg-config))
     (home-page "https://sr.ht/~jetomit/avp")
     (synopsis "Aliens Versus Predator game engine")
     (description "Unofficial Linux port of the game engine for the Rebellion