child_process: define EACCES as a runtime error

[gireeshpunathil]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Access permission on the target child is currently thrown as an exception. Bring this under the runtime error definition, much like ENOENT and friends.

Fixes: nodejs/help#990

#cat 990.js

require('child_process').spawn(process.argv[2]).on('error', (e) => console.log(e.code))

#node 990.js ./a.out
ENOENT
#touch a.out
#l a.out
-rw-r--r-- 1 gireesh staff 0 Mar 12 13:41 a.out

#node 990.js ./a.out

internal/child_process.js:323
    throw errnoException(err, 'spawn');
    ^

Error: spawn EACCES
    at _errnoException (util.js:1022:11)
    at ChildProcess.spawn (internal/child_process.js:323:11)
    at Object.exports.spawn (child_process.js:502:9)
    at Object.<anonymous> (/users/gireesh/990.js:1:88)
    at Module._compile (module.js:643:30)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)
    at tryModuleLoad (module.js:499:12)
    at Function.Module._load (module.js:491:3)
    at Function.Module.runMain (module.js:684:10)

while the the definition of runtime errors can be arguable (anything after fork vs. anything after the exec), EACCES belongs to the same group of ENOENT, by all means.

With this fix:
#node 990.js ./a.out
EACCES

[gireeshpunathil]

CI: https://ci.nodejs.org/job/node-test-pull-request/13641/

[gireeshpunathil]

landed as 11b6c0d , thanks.

[targos]

semver-patch or major?

[gireeshpunathil]

@targos - It changes the external behavior, I don't know how to classify it though.

[ An executable file that has come for launch through child_process.spawn* / exec* family of functions, and the current user does not have execute permission on it, will throw exception prior to this PR. With this, it will now be contained in the child_process handles' error handler. ]

[bnoordhuis]

I've conservatively tagged this semver-major.