cmake: Update the simulation script for Spike

Update the simulation script to work with the latest QEMU(v5.0.0).

Signed-off-by: Siwei Zhuang <siwei.zhuang@data61.csiro.au>

convert license headers to SPDX

Includes license review of 3rd-party files, adding missing upstream
headers, and moving the UNSW OZPLB license into its own file rather
than replicating it in the header.

simulation: added optional extra args to qemu

It's now possible to set qemu_sim_extra_args to pass extra arbitrary
arguments to qemu when generating simulate script.

trivial: Style changed files

trivial: Fix typo

simulation: Create helper to launch gdb instance

This helps improve the usability of the gdb changes introduced in the
simulate scripts.

simulation: Add QEMU commands for GDB in scripts

This adds the option for the simulate scripts to tell QEMU to wait for a
GDB instance to connect to it before starting.

Co-authored-by: Jonas Claeson <jonas.cl@protonmail.com>

Added hyp support for qemu-arm-virt simulation

The simulate script is now generated with virtualization=on iff the
KernelArmHypervisorSupport is activated.

Added the new virt platform

This commit adds the new virt platform to the build system's application
settings as well as the simulation generation.

CMake: include KERNEL_HELPERS_PATH for RequireFile

RequireFile is defined in the kernel helpers CMake file that is stored
under KERNEL_HELPERS_PATH.

simulation.cmake: Use RequireFile for script paths

RequireFile adds error checking and marks the cache variables as
advanced.

CMake: Add comment to explain qemu serial flags

added comment to explain '-serial null -serial mon:stdio' flag

CMake: Remove gdb flag from simulation line

-s is shorthand for -gdb tcp::1234. We don't need to pass this by
default.

CMake: Refactor helpers to be included on demand

As more helper files get added it becomes more expensive to include them
all in common.cmake. We instead add them to the CMAKE_MODULE_PATH and
allow them to be imported as CMake modules. Adding global include guards
allows them to be imported multiple times without processing every time.

CMake: Remove gdb flag from RISC-V simulation line

-s is shorthand for -gdb tcp::1234. We don't need to pass this by
default.

Produce fallback simulation script portably

"echo -e" (to interpret C-style backslash escape sequences) is not
portable and in fact does not work on Debian buster.

The generated shell script looked like this:

-e #!/bin/sh
echo ${error} && exit -1

...which did not work.

A negative exit status is also not portable.

So:
* Switch to the portable printf.
* Exit with status 1 instead of -1.
* Add a layer of backslash escaping to achieve correct script
generation.

trivial: style this repo

cmake: Move simulation functions into own file