ignore files for clangd

Change-Id: I562e9965468c7a6ce538e3d02dcdfc9d8f6123b9
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/13321
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Brett Wilson <brettw@chromium.org>

.gitignore

diff --git a/.gitignore b/.gitignore
index 4c20aff..aa227f6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,6 +33,7 @@
 !Android.mk
 .*.sw?
 .DS_Store
+.cache
 .cipd
 .classpath
 .cproject
@@ -44,6 +45,7 @@
 .pydevproject
 .recipe_deps
 .checkstyle
+compile_commands.json
 cscope.*
 out/
 GPATH