Non-SFI Mode: Centralise test whitelists; move to Scons

Non-SFI Mode: Centralise test whitelists; move to Scons

Simplify the whitelists of tests to run under Non-SFI Mode by moving
them to Scons.  Add "nonsfi_tests{,_irt}" test suites.

This allows us to remove the duplication between buildbot_pnacl.{sh,py},
and the internal duplication within those files between lists of
IRT-based and non-IRT-based tests.

Make some changes to allow tests to be run consistently as both
IRT-based and non-IRT-based tests:

 * Add a getpid() syscall wrapper.
 * Fix clock_getres() when it's given a NULL pointer.

Disable signal test under QEMU via nacl.scons rather than via having a
difference between buildbot_pnacl.{sh,py}.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3851
TEST=nonsfi_tests{,_irt} + trybots
R=dschuff@chromium.org, hidehiko@chromium.org

Committed: https://src.chromium.org/viewvc/native_client?view=rev&revision=13573

[Derek Schuff, 2014-07-31 16:15:16]

LGTM. Please commit ASAP, as I have 2 changes now blocked on this that if
possible i'd like to get in before my desktop disappears this afternoon :)

[hidehiko, 2014-07-31 16:59:34]

LGTM, assuming all tests (incl hw arm bot) pass.

[Mark Seaborn, 2014-07-31 17:59:42]

Committed patchset #4 manually as r13573 (presubmit successful).

[Mark Seaborn, 2014-07-31 18:01:59]

I rebased this on hamaji's change
(https://src.chromium.org/viewvc/native_client?revision=13570&view=revision) and
manually re-tested.  I didn't want to wait 1-2 hours for the trybots to run
again since Derek wanted this committed soon.