Building OpenJDK that matches OracleJDK update

[Brian Toal]

I'm trying to figure out how to build the OpenJDK so that it's at parity
with the OracleJDK version.

For example I want to build OpenJDK that is the equivalent of 8u45.
Appreciate if someone could point me into the correct direction to any
literature that explains how this is done.

I've see it's possible to clone 8u40, but not 8u45

hg clone http://hg.openjdk.java.net/jdk8u/jdk8u40 jdk8u40

as I get 404's when trying to clone.