Sanitize synthexec helper (issue #52)
Sanitize synthexec helper (issue #52)

Per Matt Dillon's recommendation:
1) While there should no be any file descriptor past 2 open prior to the
execv command,
go ahead and guarantee it by executing closefrom (3) before the fork.
2) It's expected that STDIN, STDOUT, STDERR are all open when synthexec.
If that is
not true, the fd would return 0, 1, or 2 which indicates something went
wrong.  Go
ahead and test for that and eject if fd <= 2

jrmarino/synth,jrmarino/synth,jrmarino/synth,jrmarino/synth