Allow setting compilation database directory

[wolfpld]

This change adds a configuration entry that allows you to specify a custom location for the compile_commands.json file. For example, this might be necessary if you are using the VS Code Meson extension, which by default uses builddir as the build directory containing the above file.

Or imagine you have a single workspace where you have two separate build directories with different feature flags enabled. Perhaps you are targeting multiple platforms in this way? You want to be able to quickly switch between these different configurations.

While you can achieve the same result by adding --compile-commands-dir=... to the clangd.arguments configuration variable, this is hardly discoverable by users. Adding a separate variable with a proper description will better expose the functionality.

Also, while clangd.compilationDatabaseDirectory is currently restricted to trusted workspaces only, a proper check on the validity of the specified path would allow this restriction to be removed, which cannot be said for the more general clangd.arguments parameter. Unfortunately, the VS Code API does not seem to expose any functionality to do this, and I am not able to do it safely myself.

[tristan957]

For what it is worth, you can pass the directory containing the compile_commands.json to clang through the clangd.arguments setting.

[wolfpld]

Yes, this is what I want to work on today. The downside is that we will overwrite any custom settings the user may have provided.

[tristan957]

@wolfpld I agree that settings the compilation database is a little bit more special than the other arguments.