fix: FreeBSD port build issues (#1325)

Author: braindigitalis

mlspp/lib/hpke/CMakeLists.txt

@@ -55,3 +55,9 @@ include_directories("${CMAKE_CURRENT_SOURCE_DIR}/../../lib/mls_vectors/include")
 include_directories("${CMAKE_CURRENT_SOURCE_DIR}/../../lib/tls_syntax/include")
 # For nlohmann/json.hpp
 include_directories("${CMAKE_CURRENT_SOURCE_DIR}/../../../include")
+if (DPP_USE_EXTERNAL_JSON)
+	add_compile_definitions(DPP_USE_EXTERNAL_JSON)
+	message("-- HPKE using external nlohmann::json")
+else()
+	message("-- HPKE using DPP nlohmann::json")
+endif()

src/dpp/dave/persisted_key_pair_generic.cpp

@@ -30,9 +30,10 @@
 #include <functional>
 #include <iostream>
 #ifdef _WIN32
-#include <io.h>
+	#include <io.h>
 #else
-#include <unistd.h>
+	#include <unistd.h>
+	#include <sys/stat.h>
 #endif
 #include <fcntl.h>
 #include <bytes/bytes.h>