tools: fix C++ import checker argument expansion

Makefile assumes that it can pass a list of files to the import
checker, whereas the import checker expects a single argument
that is interpreted as a blob.

Fix that mismatch by accepting multiple arguments in the import
checker.

Refs: https://github.com/nodejs/node/pull/34565

PR-URL: https://github.com/nodejs/node/pull/34582


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>