Add USES_TERMINAL option for custom commands

Teach the add_custom_command and add_custom_target commands a new
USES_TERMINAL option.  Use it to tell the generator to give the command
direct access to the terminal if possible.

Help/command/add_custom_command.rst

@@ -18,7 +18,8 @@ The first signature is for adding a custom command to produce an output::
                      [IMPLICIT_DEPENDS <lang1> depend1
                                       [<lang2> depend2] ...]
                      [WORKING_DIRECTORY dir]
-                     [COMMENT comment] [VERBATIM] [APPEND])
+                     [COMMENT comment]
+                     [VERBATIM] [APPEND] [USES_TERMINAL])
 
 This defines a command to generate specified ``OUTPUT`` file(s).
 A target created in the same directory (``CMakeLists.txt`` file)
@@ -120,6 +121,11 @@ The options are:
   as a file on disk it should be marked with the :prop_sf:`SYMBOLIC`
   source file property.
 
+``USES_TERMINAL``
+  The command will be given direct access to the terminal if possible.
+  With the :generator:`Ninja` generator, this places the command in
+  the ``console`` pool.
+
 ``VERBATIM``
   All arguments to the commands will be escaped properly for the
   build tool so that the invoked command receives each argument
@@ -151,7 +157,8 @@ target is already built, the command will not execute.
                      COMMAND command1 [ARGS] [args1...]
                      [COMMAND command2 [ARGS] [args2...] ...]
                      [WORKING_DIRECTORY dir]
-                     [COMMENT comment] [VERBATIM])
+                     [COMMENT comment]
+                     [VERBATIM] [USES_TERMINAL])
 
 This defines a new command that will be associated with building the
 specified target.  When the command will happen is determined by which

Help/command/add_custom_target.rst

@@ -9,7 +9,8 @@ Add a target with no output so it will always be built.
                     [COMMAND command2 [args2...] ...]
                     [DEPENDS depend depend depend ... ]
                     [WORKING_DIRECTORY dir]
-                    [COMMENT comment] [VERBATIM]
+                    [COMMENT comment]
+                    [VERBATIM] [USES_TERMINAL]
                     [SOURCES src1 [src2...]])
 
 Adds a target with the given name that executes the given commands.
@@ -74,6 +75,11 @@ The options are:
   is platform specific because there is no protection of
   tool-specific special characters.
 
+``USES_TERMINAL``
+  The command will be given direct access to the terminal if possible.
+  With the :generator:`Ninja` generator, this places the command in
+  the ``console`` pool.
+
 ``WORKING_DIRECTORY``
   Execute the command with the given current working directory.
   If it is a relative path it will be interpreted relative to the