presets: Add macro for "jobs" in presets
Background One benefit of presets is to tell cmake how to build it, it can be loaded by IDE or simple CLI build. In should also include how many parallel build it wants to do, by using user-OS-defined macros such as $(nproc) for linux. Windows may be okay since the Visual Studio has it's own parallel build setting and I think it automatically use all the core, but not 100% sure.
Current implementation Currently, "jobs" parameter in preset cannot use macro, meaning that it has to be a set to a fixed number. As a result, when building in IDE such as Visual Studio Code with cmake extension, it will only build single threaded unless user-space config is done somewhere else. This is very inconvenient to share among teams since we don't want to build single threaded.
Suggestion allow macro to be use in "jobs".
Potential difficulty I am not sure how it can be done since "jobs" is an integer type, would changing the type causing backward incompatibility issue? Would it be possible to add a new one like "jobsMacro" that will only be used when "jobs" does not exist? Not sure.