This warning was useful when users previously needed to manually
build the kernel and run this script.

Now you can simply do 'make compile_commands.json', which updates
all the necessary build artifacts and automatically creates the
compilation database. There is no more worry for a mistake like
"Oh, I forgot to build the kernel".

Now, this warning is rather annoying.

You can create compile_commands.json for an external module:

  $ make M=/path/to/your/external/module compile_commands.json

Then, this warning is displayed since there are usually less than
300 files in a single module.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>