RFR 8208524: IntelliJ support broken since 2018.2

[Maurizio Cimadamore]

Hi,
support for IntelliJ projects (both langtools specific and JDK-wide) is 
broken by a fix in the latest IntelliJ 2018.2, which prevents parsing of 
ant files inside the .idea configuration folder.

The solution is to copy the ant file into some sub-folder of the build 
folder (I've called it .idea-support for now), which fixes the issue.

I have more changes in the pipeline to improve the IntelliJ support, 
including one which fixes the -o flag (e.g. JDK-8180794) - that's to say 
that I know that this patch adds more assumptions on the location of the 
build folder, but we have plans to remove such assumptions in due 
course. In the short term, priority is to keep support working.

Webrev:

http://cr.openjdk.java.net/~mcimadamore/8208524/

Cheers
Maurizio