RFR: JDK-8154841: Let different Jib profiles have different default make targets

[Erik Joelsson]

Currently all Jib profiles define the default make target configure arg 
to be "all". While this works ok for our current main profiles, it's a 
bit crude and will not work well when start introducing more specialized 
profiles. I have implemented a way of specifying the list of default 
make targets much like configure arguments are specified today, by 
adding a function that converts this new field on a profile into the 
corresponding configure arg.

To demonstrate the feature I have also disable building of docs on most 
profiles. The docs build is very platform independent and we are 
currently wasting quite a bit of time letting every build, both release 
and debug, build docs. With these changes, only linux-x64 builds docs by 
default. Note that this applies to distributed build scenarios, like 
JPRT and RE at Oracle. A developer wanting to build docs may still do so 
by typing "make docs".

While tweaking the docs build, I also corrected the dependencies that 
were recently introduced for the new open docs bundle. It seems I was 
sloppy with the review on that change.

Bug: https://bugs.openjdk.java.net/browse/JDK-8154841
Webrev: http://cr.openjdk.java.net/~erikj/8154841/webrev.top.01/

/Erik