CPack: use IsOn instead of IsSet for boolean CPack options

The CPackComponent macros specifically set CPack options to FALSE
which CPack previously interpreted to mean "true".
Ninja: job pool support for compiling and linking

Could be tested by setting the environment
variable NINJA_STATUS=[%r]
Merge topic 'ninja-compile-link-pool' into next

a9bf906 Ninja: job pool support for compiling and linking
Merge topic 'make-cpack-options-boolean' into next

5bc6444 CPack: use IsOn instead of IsSet for boolean CPack options