build: add workaround for V8 builds

V8's build toolchain is not compatible with Python 3 and the CI job
that tests V8 needs to be run with Python 2. Add a fallback to
`find_executable` from `distutils.spawn` to allow the configure
script to run in the V8 test job.

PR-URL: https://github.com/nodejs/node/pull/38632


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>