Use libffi and openssl in all environment variables.

component/python-cryptography/buildout.cfg

@@ -14,6 +14,6 @@ environment = python-cryptography-env
 
 [python-cryptography-env]
 PATH = ${pkgconfig:location}/bin:%(PATH)s
-PKG_CONFIG_PATH = ${libffi:location}/lib/pkgconfig
-LD_LIBRARY_PATH = ${libffi:location}/lib
-CPATH = ${openssl:location}/include
+PKG_CONFIG_PATH = ${libffi:location}/lib/pkgconfig:${openssl:location}/lib/pkgconfig
+LD_LIBRARY_PATH = ${libffi:location}/lib:${openssl:location}/lib
+CPATH = ${libffi:location}/include:${openssl:location}/include