ci: On OS X, install openssl brew package to standard locations ("link" it)

Without "linking", ci scripts installs homebrew package into the 
customized location and does not create links in the standard places. 
As a result, the build will be using the system-provided openssl, which 
is old and does not support all features needed by ndn-cxx.

Change-Id: I3a7d4b7dbb8e00789846f6ec970039a5cf5368bc
diff --git a/.jenkins.d/00-deps.sh b/.jenkins.d/00-deps.sh
index 241ffe5..d50857c 100755
--- a/.jenkins.d/00-deps.sh
+++ b/.jenkins.d/00-deps.sh
@@ -13,6 +13,7 @@
     brew update
     brew upgrade
     brew install boost pkg-config cryptopp $EXTRA_FLAGS
+    brew link --force openssl
     brew cleanup
 fi