cmake: Include OpenSSL libraries in static linking

CMakeLists.txt

@@ -177,8 +177,6 @@ if(MINGW)
   list(REMOVE_ITEM CMAKE_CXX_IMPLICIT_LINK_DIRECTORIES ${DEFLIB})
 endif()
 
-set(ORIG_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
-
 if(STATIC)
   if(MSVC)
     set(CMAKE_FIND_LIBRARY_SUFFIXES .lib .dll.a .a ${CMAKE_FIND_LIBRARY_SUFFIXES})

external/CMakeLists.txt

@@ -76,11 +76,12 @@ endif()
 find_package(Unbound)
 
 if(NOT UNBOUND_INCLUDE_DIR OR STATIC)
-  # We want unbound config tests to be independent of changes made to this setting.
-  set(CURRENT_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
-  set(CMAKE_FIND_LIBRARY_SUFFIXES ${ORIG_CMAKE_FIND_LIBRARY_SUFFIXES})
+  # NOTE: If STATIC is true, CMAKE_FIND_LIBRARY_SUFFIXES has been reordered.
+  # unbound has config tests which used OpenSSL libraries, so -ldl may need to
+  # be set in this case.
+  # The unbound CMakeLists.txt can set it, since it's also needed for the
+  # static OpenSSL libraries set up there after with target_link_libraries.
   add_subdirectory(unbound)
-  set(CMAKE_FIND_LIBRARY_SUFFIXES ${CURRENT_CMAKE_FIND_LIBRARY_SUFFIXES})
 
   set(UNBOUND_STATIC true PARENT_SCOPE)
   set(UNBOUND_INCLUDE "${CMAKE_CURRENT_SOURCE_DIR}/unbound/libunbound" PARENT_SCOPE)

external/unbound/CMakeLists.txt

@@ -40,6 +40,12 @@ if (APPLE)
 endif()
 
 find_package(OpenSSL REQUIRED)
+if(STATIC)
+  if(UNIX)
+    set(OPENSSL_LIBRARIES "${OPENSSL_LIBRARIES};${CMAKE_DL_LIBS}")
+  endif()
+endif()
+
 find_package(Threads)
 
 include(configure_checks.cmake)