Add .ccls-cache to .gitignore

This directory is created by ccls (language server for C++ and others).

R=sigurds@chromium.org

Change-Id: I2413921ca896ad2003fcfd10fdadb739f1af18c8
Reviewed-on: https://chromium-review.googlesource.com/c/1487151Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59855}

.gitignore

@@ -23,6 +23,7 @@
 *~
 .#*
 .*.sw?
+.ccls-cache
 .cpplint-cache
 .cproject
 .d8_history