This brings the patch step into line with all the others which already
had their own `USES_TERMINAL_<step>` keyword. All steps (including
patch) already have their own `LOG_<step>` keyword too, so the lack of
`USES_TERMINAL_PATCH` was inconsistent.
Added new USES_TERMINAL option to the ExternalProject_Add_Step
function. This option passes USES_TERMINAL to the underlying
add_custom_command call so that the Ninja console pool is used.
Also, corresponding new USES_TERMINAL_<step> options were added
to the ExternalProject_Add function.
Justification: if using Ninja with a CMake superbuild, it's often
desirable to limit the superbuild to ONE sub-Ninja process at a
time to avoid oversubscribing the CPU. Using the console pool also
makes it easy to monitor the progress of the sub-Ninja process.
Independent USES_TERMINAL_<step> arguments are passed to
ExternalProject_Add instead of one USES_TERMINAL argument that
controls everything. Users may wish to run some steps in parallel
but not others (e.g. parallelize configure but not build).
Craig Scott