cassandra: create 'upstream/current' symlink

It points to the directory used by last 'make'. This is needed to
reliably determine the directory with casandra files. Version changes
can leave old directories behind and we want to avoid calling 'make
clean'.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
ruby: fix compile error with -j option

Currently ruby module causes build error on make image=ruby -jN.
This is caused from openssl Makefile, and missing dependency on EXT_* targets.

Signed-off-by: Takuya ASADA <syuu@cloudius-systems.com>