Does not return if the command is not executable by user's primary group

[Manatsawin Hanmongkolchai]

Steps to reproduce:

1. sudo chmod o-x /usr/bin/make
2. sudo chown root:sudo /usr/bin/make
3. Run a node-gyp build from a user who is a member of group sudo, but sudo is not his primary group

(Tested on Debian 6.0.8)

node-gyp will complain about missing make, even if make is in fact executable by current user.

Related SO

[isaacs]

Yes, we need to check against all the results from process.getgroups() if the function is available. Patch welcome.