CI: fix linter checking non-APKBUILDs (!867)

Only check APKBUILD files

.gitlab-ci/apkbuild-linting.py

@@ -15,7 +15,7 @@ if __name__ == "__main__":
 
     issues = []
     for package in packages:
-        if "temp/" in package:
+        if "temp/" in package or "APKBUILD" not in package:
             continue
 
         result = subprocess.run(["apkbuild-lint", package], capture_output=True)