.gitignore: Add compilation database file

This file is used by clangd to use language server protocol.
It can be generated at each compile using scripts/gen_compile_commands.py.
Therefore it is different depending on the environment and should be
ignored.

Signed-off-by: Toru Komatsu <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

Author: utam0k

.gitignore

@@ -142,3 +142,6 @@ x509.genkey
 
 # Kdevelop4
 *.kdev4
+
+# Clang's compilation database file
+/compile_commands.json