nghttp: build port directory

Fixes https://github.com/espressif/esp-idf/issues/843

components/nghttp/component.mk

@@ -4,6 +4,6 @@
 
 COMPONENT_ADD_INCLUDEDIRS := port/include nghttp2/lib/includes
 
-COMPONENT_SRCDIRS := nghttp2/lib
+COMPONENT_SRCDIRS := nghttp2/lib port
 
 COMPONENT_SUBMODULES := nghttp2