llhttp: add pkg-config tester

pkgs/development/libraries/llhttp/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, cmake }:
+{ lib, stdenv, fetchFromGitHub, cmake, testers }:
 
 stdenv.mkDerivation (finalAttrs: {
   pname = "llhttp";
@@ -19,11 +19,16 @@ stdenv.mkDerivation (finalAttrs: {
     "-DBUILD_STATIC_LIBS=ON"
   ];
 
+  passthru.tests.pkg-config = testers.hasPkgConfigModules {
+    package = finalAttrs.finalPackage;
+  };
+
   meta = with lib; {
     description = "Port of http_parser to llparse";
     homepage = "https://llhttp.org/";
     changelog = "https://github.com/nodejs/llhttp/releases/tag/release/v${finalAttrs.version}";
     license = licenses.mit;
+    pkgConfigModules = [ "libllhttp" ];
     maintainers = [ maintainers.marsam ];
     platforms = platforms.all;
   };