Add spawnfd for use where fork / forkfd can't be used

In certain environments, using fork() is not recommended due to the need
for an MMU. This commit adds support for those environments, by using
posix_spawn. Limitations of this environment are:
 - we cannot reliably detect failure to exec (e.g. non-existing executable)
 - we cannot do setsid(); we do setpgrp(0, 0) instead
 - we cannot thread-safely chdir() to the requested dir

Because of the former limitation, the QProcess unit tests that rely on
failure-to-start error conditions are either skipped or marked as
expected failures. There's a non-reliable solution that is implemented
in a another commit.

This change also makes it easier to transition the QNX builds to using
fork(), which is supported from QNX Neutrino 6.6 and onwards.

Change-Id: I5cb46abf2ef8783941525d35cc991f00d2bf2d58
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions