Export public headers from libhermes

Summary:
Anything depending on libhermes needs the contents of the public
directory.

Reviewed By: jpporto

Differential Revision: D38478938

fbshipit-source-id: e00e618babc6ede6bf218fbee36a50acb5f1b218

API/hermes/CMakeLists.txt

@@ -63,7 +63,7 @@ target_link_libraries(libhermes
 target_link_options(libhermes PRIVATE ${HERMES_EXTRA_LINKER_FLAGS})
 
 # Export the required header directory
-target_include_directories(libhermes PUBLIC .. ${HERMES_JSI_DIR})
+target_include_directories(libhermes PUBLIC .. ../../public ${HERMES_JSI_DIR})
 
 set_target_properties(libhermes PROPERTIES
   # Avoid becoming liblibhermes (and there's already a target called 'hermes')