kunit: tool: Use qemu-system-i386 for i386 runs

We're currently using the x86_64 qemu for i386 builds. While this is not
incorrect, it's probably more sensible to use the i386 one, which will
at least fail properly if we accidentally were to build a 64-bit kernel.

Signed-off-by: David Gow <davidgow@google.com>
Tested-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: tool: stop using a shell to run kernel under QEMU

Note: this potentially breaks custom qemu_configs if people are using
them! But the fix for them is simple, don't specify multiple arguments
in one string and don't add on a redundant ''.

It feels a bit iffy to be using a shell in the first place.

There's the usual shenanigans where people could pass in arbitrary shell
commands via --kernel_arg (since we're just adding '' around the
kernel_cmdline) or via a custom qemu_config.
This isn't too much of a concern given the nature of this script (and
the qemu_config file is in python, you can do w/e you want already).

But it does have some other drawbacks.

One example of a kunit-specific pain point:
If the relevant qemu binary is missing, we get output like this:
> /bin/sh: line 1: qemu-system-aarch64: command not found
This in turn results in our KTAP parser complaining about
missing/invalid KTAP, but we don't directly show the error!
It's even more annoying to debug when you consider --raw_output only
shows KUnit output by default, i.e. you need --raw_output=all to see it.

Whereas directly invoking the binary, Python will raise a
FileNotFoundError for us, which is a noisier but more clear.

Making this change requires
* splitting parameters like ['-m 256'] into ['-m', '256'] in
kunit/qemu_configs/*.py
* change [''] to [] in kunit/qemu_configs/*.py since otherwise
QEMU fails w/ 'Device needs media, but drive is empty'
* dropping explicit quoting of the kernel cmdline
* using shlex.quote() when we print what command we're running
so the user can copy-paste and run it

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: tool: add support for QEMU

Add basic support to run QEMU via kunit_tool. Add support for i386,
x86_64, arm, arm64, and a bunch more.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: David Gow <davidgow@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>