gitignore .clangd

Add the new location where clangd stores it's index to gitignore.

Change-Id: I10381131d4adfcbbaa4f3ebf7705f5e84b47f353
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108411
Reviewed-by: Samir Jindel <[email protected]>
Commit-Queue: Daco Harkes <[email protected]>

Author: dcharkes

.gitignore

@@ -55,6 +55,9 @@ compile_commands.json
 # GDB files
 .gdb_history
 
+# Clangd files
+.clangd
+
 # Built by chromebot and downloaded from Google Storage
 client/tests/drt