Actually fix restarting the LSP in :BuildDir job callback

plugin/build.lua

@@ -31,9 +31,12 @@ function build.set_dir(dirname)
 
       -- Restart clangd language server
       on_exit = function()
-        vim.cmd('LspStop')
-        vim.cmd('LspStart')
+        -- This is a callback so doesn't run on the main thread which causes
+        -- issues for running commands, so schedule that on the main thread.
+        vim.schedule(function()
+          vim.cmd('LspRestart')
           echo('Build directory selected: ' .. dirname, 'DiagnosticInfo')
+        end)
       end,
 
       -- Display any error messages to the user