test: backport use executable in spawn() test

Backport 10703774

 from the v0.12 branch.

Currently, the test-child-process-spawn-typeerror.js is
calling execFile() on a JavaScript source file, which is
causing failures on Windows. This commit switches to calling
spawn() on an actual executable.

Fixes #8930.

Signed-off-by: Julien Gilli <julien.gilli@joyent.com>