lkmc v2-rc

Unsquashed version at v2-rc-unsquashed, but that cannot be merged as it
breaks bisects at several points. All bugs will not bisect to this
humongous change.

It all started with a conversion of the Bash scripts to Python, mainly
because I couldn't stand not being able to properly use --options for
run which has a million options.

Then since that required a full testing, I decided to do all the
refactorings that I had in mind at once, and so I did and it became
v2-rc.

This is the largest patch I have ever done! OMG a few weeks of extra time.
I'm never writing a Bash script for anything that starts getting big again.

Some of the features are:

* separate build-qemu and build-gem5 commands
* common: convert scripts to python. Add --option for everything
* rename build to build-buildroot now that we are splitting all the build
  commands, Linux kernel to follow
* move all git submodules to submodules/ and all buildroot packages to
  packages/
* refactor the out/ structure. Keep projects on toplevel, because guest
  projects separate archs and host ones don't, making a toplevel arch wrong
* do-release: rename to just release
  https://stackoverflow.com/questions/16174992/cant-get-argparse-to-read-quoted-string-with-dashes-in-it
* run: add --terminal and explain gem5 pdb
* just track the lvimrc
* store CLI kernel config fragment inside buildlroot to avoid conflicts
* gem5: document m5 initparam
* readme: make a bunch of things awesomer
* readme: fix broken refs
* parsec-benchmark: update to 75d55ac446a43c47efb1044844a108c6c330184c
  Could not fetch otherwise.
* gem5: M5_OVERRIDE_PY_SOURCE

build-qemu

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+
+import multiprocessing
+import os
+import subprocess
+
+import common
+
+parser = common.get_argparse()
+common.add_build_arguments(parser)
+parser.add_argument(
+    'extra_config_args',
+    default=[],
+    metavar='extra-config-args',
+    nargs='*'
+)
+args = common.setup(parser)
+if args.clean:
+    common.rmrf(common.qemu_build_dir)
+else:
+    os.makedirs(common.qemu_build_dir, exist_ok=True)
+    subprocess.check_call(
+        [
+            os.path.join(common.qemu_src_dir, 'configure'),
+            '--enable-debug',
+            '--enable-trace-backends=simple',
+            '--target-list={}-softmmu'.format(args.arch),
+            '--enable-sdl',
+            '--with-sdlabi=2.0',
+        ] +
+        args.extra_config_args,
+        cwd=common.qemu_build_dir
+    )
+    subprocess.check_call(
+        [
+            'make',
+            # TODO factor with build.
+            '-j', str(multiprocessing.cpu_count()),
+        ],
+        cwd=common.qemu_build_dir
+    )