cspec Makefile: add target for kernel source.

Adds a target name that ensures that the preprocessed kernel source
is up to date, but doesn't do any other work. This avoids confusion
when doing a check of source compatibility in building the seL4 input
for graph-refine.

riscv: setup cspec build for L4V_ARCH=RISCV64

C parser and word setup copied from X64

cspec: fix make dependency breakage when CMake command fails

Once again, with feeling. This commit uses a dummy file as the CMake
dependency, to avoid re-running the kernel build in parallel.

Revert "cspec: fix make dependency breakage when CMake command fails"

This reverts commit 16356963878d82c6c227d58e00c04807e1d572f0.

Unconditionally cleaning and invoking the kernel build system turns out
to be a bad idea; it breaks when multiple builds are run in parallel.

cspec: fix make dependency breakage when CMake command fails

cspec: Pass SORRY_BITFIELD_PROOFS to kernel build

SORRY_BITFIELD_PROOFS is potentially specified as an environment variable, which does not
implicitly become a CMake variable, and so must be explicitly constructed.

cspec: Reconfigure kernel build on sources change

Previously the kernel build would be reconfigured only if the explicit config file
passed in -C changed, but this file is very minimal and is only used when a variable
needs to be set to a non default value. As a result when default values are added
or changed a reconfigure will not be triggered.

This commit pays higher build times (by completely purging the build directory) in
order to more reliably capture reconfigures and rebuilds.

cspec: Remove redundancy in build rules and theory files for c-kernel builds

Removes files that were duplicated in cspec/$L4V_ARCH directories to exist directly in
the cspec directory and contain $L4V_ARCH switches where needed. This allows for a single
Makefile for building the C kernel and the KernelInc_C theory, which is different between
architectures, to still exist per L4V_ARCH.

As the build location of the C kernel, and the resulting kernel_all.c_pp artifact, is
moved this change needs to be reflected in all the theory files that refer to it.

x64 cspec: add x86-64 kernel config for building CKernel

This should be the right configuration. However, the c-parser does not
yet successfully parse the preprocessed source.

arm-hyp: configure kernel Makefile for L4V_ARCH=ARM_HYP

Set as required for TK1 platform.

l4v-sabre: fix refine

cspec: build: avoid re-entering isabelle via dash-0.5.8

paramatrised abstract and haskell specs over L4V_ARCH

Haskell translator was modified to support multiple translations
of the haskell, with different build parameters.

regression: remove forceful build options from CSpec makefiles. They don't seem to be needed.

cspec: Check CPP exists and fallback on native CPP if possible.

Import release snapshot.