RFR: JDK-8027584 disable ccache by default

[Steven R. Loomis]

Late to the party, but please note that the README-builds.html *still*
says that  ccache is great and you should install it. Doesn't mention
*anything* about ccache being off by default or `--enable-ccache` being
needed.  In fact, configure actively disables ccache if you use a
symlink to ccache for gcc.

I'll file a ticket if need be to fix the docs. Bit by this change-
ccache does much, much more good than harm for people who are making
small changes to big projects. Not going to argue the default, but
please keep the capability around if possible.

-s (doing an overnight build to prime the ccache pump)

On 1/28/2014 3:31 PM, Magnus Ihse Bursie wrote:
> Bug: https://bugs.openjdk.java.net/browse/JDK-8027584
>
> While ccache can be used to speed up recompilations, there are also
> several issues with ccache. Old versions does not work correctly for
> the jdk (we try to detect that). It does not work well on other
> platforms than Linux; on Windows it does not work at all. Nevertheless
> is ccache enabled on Windows if it is installed, which it apparently
> tends to be with Cygwin nowadays, requiring the use of
> --disable-ccache to avoid compilation failure.
>
> In many circumstances ccache also does not provide any performance
> benefit. For instance, new compilations gets a performance hit. Only
> recompilations benefits.
>
> It is better to turn this upside down. This patch makes ccache
> disabled by default, on all platforms. If you want ccache and are sure
> you are in a situation that benefits from it, then you can enable it.
> It also removes the output in configure hinting that ccache should be
> used.
>
> WebRev:
> http://cr.openjdk.java.net/~ihse/JDK-8027584-disable-ccache-by-default/webrev.01
>
> /Magnus