Allow selecting a specific output for syntax coloring

[SIGFUN]

clangd's compilation database command schema supports an output field which labels the command's output. This is used to disambiguate different processing modes for the same source file (e.g. a single source file that builds release vs. debug variants which have different compiler flags). It'd be great if the Sublime LSP package could index all the outputs present in the compile_commands.json database and allow me to switch among all the processing modes it discovered.

I've got an issue open with clangd to also do something with this field (it's documented, but apparently unused), but they also said that the LSP package could do this itself, and I think they're right.