[CMake] parallel builds for ctest

[Bill Hoffman]

Alan W. Irwin wrote:
> On 2008-02-16 12:38-0500 Bill Hoffman wrote:
> 
>> [...]parallel ctest is on the todo list for this year.  Most likely  
>> it will be ctest -j N.   We can not depend on the make system to do 
>> the parallel stuff, and ctest -j would be useful for all generators.
> 
> That's excellent news!  The execution of the PLplot tests actually take
> about the same time to run as (non-parallel) building of PLplot itself. Now
> we are doing our builds in parallel, convenient parallel testing will be
> most welcome as well, and I look forward to trying out that new ctest
> functionality once you are ready.
> 

As a work around until we get it done, you can do something like this:

ctest -I1,10
ctest -I11,20

And run each of those in a different shell.

-Bill