Enable LoongArch support in kunit.

Example:

	$ ./tools/testing/kunit/kunit.py run --arch=loongarch --cross_compile=$CROSS_COMPILE
	[13:32:45] Configuring KUnit Kernel ...
	[13:32:45] Building KUnit Kernel ...
	Populating config with:
	$ make ARCH=loongarch olddefconfig CROSS_COMPILE=$CROSS_COMPILE
	Building with:
	$ make all compile_commands.json ARCH=loongarch --jobs=8 CROSS_COMPILE=$CROSS_COMPILE
	[13:32:48] Starting KUnit Kernel (1/1)...
	[13:32:48] ============================================================
	Running tests with:
	$ qemu-system-loongarch64 -nodefaults -m 1024 -kernel .kunit/arch/loongarch/boot/vmlinux.elf -append 'kunit.enable=1 console=ttyS0 kunit_shutdown=poweroff' -no-reboot -nographic -serial stdio -machine virt -device pvpanic-pci -cpu max

	...

	[13:33:14] ============================================================
	[13:33:14] Testing complete. Ran 493 tests: passed: 453, skipped: 40
	[13:33:14] Elapsed time: 28.862s total, 0.002s configuring, 2.526s building, 26.302s running
	

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
Thomas Weißschuh (4):
      LoongArch: Don't crash in stack_top() for tasks without vDSO
      kunit: qemu_configs: add LoongArch config
      kunit: tool: Allow overriding the shutdown mode from qemu config
      kunit: qemu_configs: loongarch: Enable shutdown

 arch/loongarch/kernel/process.c               | 16 +++++++++-------
 tools/testing/kunit/kunit_kernel.py           |  4 +++-
 tools/testing/kunit/qemu_configs/loongarch.py | 19 +++++++++++++++++++
 3 files changed, 31 insertions(+), 8 deletions(-)
---
base-commit: 6485cf5ea253d40d507cd71253c9568c5470cd27
change-id: 20241014-kunit-loongarch-98a5b756e818

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>