Make usage of Conan provided OpenSSL transparent

Signed-off-by: Jeroen Koekkoek <jeroen@koekkoek.nl>

src/cmake/modules/FindOpenSSL.cmake

@@ -0,0 +1,34 @@
+#
+# Copyright(c) 2006 to 2018 ADLINK Technology Limited and others
+#
+# This program and the accompanying materials are made available under the
+# terms of the Eclipse Public License v. 2.0 which is available at
+# http://www.eclipse.org/legal/epl-2.0, or the Eclipse Distribution License
+# v. 1.0 which is available at
+# http://www.eclipse.org/org/documents/edl-v10.php.
+#
+# SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+#
+if(TARGET CONAN_PKG::OpenSSL)
+  add_library(OpenSSL INTERFACE IMPORTED) #ALIAS CONAN_PKG::OpenSSL)
+  target_link_libraries(OpenSSL INTERFACE CONAN_PKG::OpenSSL)
+  set(OPENSSL_FOUND TRUE)
+else()
+  # Loop over a list of possible module paths (without the current directory).
+  get_filename_component(DIR "${CMAKE_CURRENT_LIST_DIR}" ABSOLUTE)
+
+  foreach(MODULE_DIR ${CMAKE_MODULE_PATH} ${CMAKE_ROOT}/Modules)
+    get_filename_component(MODULE_DIR "${MODULE_DIR}" ABSOLUTE)
+    if(NOT MODULE_DIR STREQUAL DIR)
+      if(EXISTS "${MODULE_DIR}/FindOpenSSL.cmake")
+        set(FIND_PACKAGE_FILE "${MODULE_DIR}/FindOpenSSL.cmake")
+        break()
+      endif()
+    endif()
+  endforeach()
+
+  if(FIND_PACKAGE_FILE)
+    include("${FIND_PACKAGE_FILE}")
+  endif()
+endif()
+