[PATCH] Allow usage of external zlib copy

[Phil Race]

Diego 'Flameeyes' Pettenò wrote:
> Most distributions have policies about using external copies of
> libraries whenever possible. OpenJDK ships with a series of libraries
> that are usually available on a system, like zlib and jpeg, thus
> breaking such a policy.
>
> The attached patch tries to correct part of this by letting use of
> external zlib copy when passing EXTERNAL_ZLIB=true at the make process.
>
> I'm also gonna work on a similar patch to use external jpeg library
> (that will likely depend on this one because of some of the files
> touched being the same).
>   
The JDK's libjpeg is not the standard  IJG one. It has additional stuff 
in it and exposes only the
symbols needed by the JDK. So in no way is it interchangeable.

-phil.