Allow path to OpenSSL to be passed in to CURL build.

We will use this to pass in the path to BoringSSL.

Change-Id: Ib17078dc0027535d4d121c025d001a9a8fcd7937
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f6429e7..8528038 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,6 +39,7 @@
 
 include_directories("include")
 include_directories("lib")
+include_directories(BEFORE SYSTEM  ${OPENSSL_INCLUDE_DIR})
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 add_library(curl
   "lib/amigaos.c"