tools: add compile_commands to ignore file

Yash Ladha · yashLadha · commit 5da69f6c73ee · 2022-01-18T21:17:34.000+05:30
For developing c++ source files, clangd generates an index file for
project via `./configure -C`. We can safely ignore the file from
tracking.
diff --git a/.gitignore b/.gitignore
@@ -159,3 +159,6 @@ install_manifest.txt
 __pycache__
 .DS_Store
 *~
+
+# === Rules for C++ development ===
+compile_commands.json
