When building an OF 0.8.4 project with Xcode 7, you may see the following error:
'openssl/opensslconf.h' file not found
To fix this, open the file
libs/openFrameworksCompiled/project/osx/ and add the following line at the bottom:
USER_HEADER_SEARCH_PATHS = "$(OF_PATH)/libs/openssl/include"
If you understand the .xcconfig format, a cleaner fix would be to define a
HEADER_OPENSSL variable at the top of the file, and add it to the OF_CORE_HEADERS list. The above fix should work fine, though.
EDIT: an earlier version of this post involved installing openssl with homebrew, which is not necessary.