feature request: expose more info from custom targets

[yshui]

Basic things like the name of the target, input/output file names would be really useful.

[eli-schwartz]

"Would be really useful" doesn't explain how it would be useful.

• the output filenames are already available -- see the .full_path() method
• the input filenames are already encoded in your meson.build files as arguments to custom_target() and serve no use case after the target was created
• the "name" of the target is meaningless as it's only used for display purposes

Can you give an example of where you would use information that isn't currently available?