In this test we start up a cmake script that runs a process that sleeps,
and the timeout for the script is shorter than the sleep time.  However,
in order to properly detect that the sleeping grandchild is killed when
the script times out we need to give sufficient time for the script to
start the grandchild.  Otherwise the log file for the grandchild is not
available.

On some (cygwin) builds our previous 1 second timeout for the script was
not long enough to let the interpreter load and start the grandchild.
We make the timeout time configurable by setting CTestTestTimeout_TIME
in the cache for CMake itself.  It tells the test how long to let the
script run.  The grandchild always sleeps for 4 seconds longer to ensure
a comfortable window during which the process tree can be killed.