libdpp: use Homebrew nlohmann-json

This will use a vendored version otherwise. Let's also disable automatic
detection of `vcpkg` and `conan`, and running `ldconfig` on Linux.

Author: carlocab

Formula/lib/libdpp.rb

@@ -15,14 +15,21 @@ class Libdpp < Formula
   end
 
   depends_on "cmake" => :build
+  depends_on "nlohmann-json" => :build
   depends_on "openssl@3"
   depends_on "opus"
   depends_on "pkgconf"
 
   uses_from_macos "zlib"
 
   def install
-    system "cmake", "-S", ".", "-B", "build", "-DDPP_BUILD_TEST=OFF", *std_cmake_args
+    system "cmake", "-S", ".", "-B", "build",
+                    "-DDPP_BUILD_TEST=OFF",
+                    "-DDPP_NO_CONAN=ON",
+                    "-DDPP_NO_VCPKG=ON",
+                    "-DDPP_USE_EXTERNAL_JSON=ON",
+                    "-DRUN_LDCONFIG=OFF",
+                    *std_cmake_args
     system "cmake", "--build", "build"
     system "cmake", "--install", "build"
   end