gitignore: Add .clangd and .ccls-cache

[khng]

Summary

Add residues of clangd and ccls to prevent them from being accidentally
included in a commit.

clangd and ccls are two C/C++ Language Server implementations listed in
https://microsoft.github.io/language-server-protocol/implementors/servers/ .

Sponsored by: The FreeBSD Foundation
MFC after: 3 days

[val_packett.cool]

Ideally everyone would keep that kind of stuff in their global gitignore (core.excludesfile) :)

but if we're going with this, please also add .ccls-cache/ from the sort-of more popular these days server ccls

[khng]

In D26555#591358, @greg_unrelenting.technology wrote:

Ideally everyone would keep that kind of stuff in their global gitignore (core.excludesfile) :)

but if we're going with this, please also add .ccls-cache/ from the sort-of more popular these days server ccls

Good suggestion. :)

[khng]

• Add .ccls-cache to .gitignore

[cem]

Seems fine. Is the trailing slash needed?

[khng]

Seems not, although both are directories.

[khng]

Updated. Removed trailing slash as it causes problem when symbolic links are used.