systemc: Add a script which automates building and running tests.

systemc: Add a script which automates building and running tests.

The only required option for the script is the path to a build
directory, for instance build/ARM. It uses that when running scons and
when referring to generated files (like the built versions of the
tests). It uses the location of the script itself to find source files,
like the "golden" version of outputs.

This script runs tests in three phases, compilation, running, and
then verification. By default, all three phases are run for all tests,
but which phases run and how they work can be customized by specifying
them explicitly on the command line with the --phase option.

Each time the --phase option shows up on the command line, it should
be followed by the name of the phase being specified. That both
declares that that phase should be run, and also that any subsequent
options apply to that phase, at least until the next --phase option.

Currently, only the "compile" and "execute" phases are implemented, and
only the "compile" phase has been tested at all or has any options
defined. The "compile" phase simply takes all the options it was given
and pass them on to scons. The "verify" phase simply prints a message
which says what it would have verified.

The script can list the available tests with the --list option, as
determined by the json systemc test manifest file which scons can
generate, and which the script can refresh if passed the --update-json
option. You can also specify what "flavor" of build you want to do, ie
opt, debug, fast, etc., with the --flavor option. Only one flavor can
be tested at a time, but that should be the desired behavior most of
the time. If multiple flavors need to be tested, the script can be
invoked multiple times.

Finally, there is a --filter option which accepts a python expression
as a string. That expression is evaluated in the namespace of the
properties of each test in the json file, and if it returns true then
that test is run. For instance, to verify only compile_only tests, you
would use:

systemc/tests/verify.py build/ARM --filter 'compile_only'

To test only compile_only tests named bob, you would run this:

systemc/tests/verify.py build/ARM --filter \
    'compile_only && name ="bob"'

Also included is a simple config.py which is the beginning of a config
which will run the systemc regression tests. Right now, all it knows
how to do is run sc_main.

Change-Id: I62666be8b1622d1355153e623b4274a939507e44
Reviewed-on: https://gem5-review.googlesource.com/10975
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>