CMake: Add missing dependency to CPPFile function

CMake: CPPFile EXACT_NAME creates a temp copy

Modified the behaviour of the EXACT_INPUT option within the
CPPFile helper function. Now named EXACT_NAME, the option
copies the input file to a temporary file. The name of the
temporary file is also passed in by the caller. This
step in necessary in getting the CPP step to correctly
depend on the targets given by the caller
(through EXTRA_DEPS). Also updated the CPP generation of the
kernel_all.i file to reflect the change.

CMake: Add get_absolute_list_source_or_binary

This function checks CMAKE_CURRENT_LIST_DIR and then calls
get_absolute_source_or_binary if the file wasn't found

cmake: Use ABSOLUTE instead of REALPATH

REALPATH was unnecessary and results in resolving symlinks in the target, although
the working directory will not have its symlink resolved. This results in very strange
paths from the base directory (which is the working directory) to the target.

cmake: Remove GenCPPCommand

This helper was ugly when written and simply should not be used over the CPPFile helper.

cmake: CPPFile New helper for just pre-processing files

This is a new version of GenCPPCommand that uses an OBJECT library intermediate to get
cmake to do 'arbitrary' compilation (by adding the -E flag) where the result does not
need to be linkable. The advantage of this over the GenCPPCommand version is there is
no need for trying to manually invoke GCC with all the correct arguments lists.

cmake: get_absolute_source_or_binary is a function

As a macro this helper would not operate as expected if output and input were defined
as the same variable. Making a function and explicitly writing into the PARENT_SCOPE
fixes this and also makes the code simpler

config: Reset options to default when enabled

This change makes values take on more intuitive and expected defaults when gradually
configuring the kernel, either programatically or through the graphic interfaces

cmake config_choice: save options in cache var

This is to make it possible to enumerate all config options instead of
just the 'valid' ones that are saved as the STRINGS property.

cmake: TOPLEVELTYPES declared as target property

TOPLEVELTYPES is not intended to be configurable by the user, rather is a reflection
on the types defined by the source. This changes the TOPLEVELTYPES argument to be
a property, allowing it to be constructed as a generator expression when generating
BF files. By being a property, and not something like a global property, it removes
the need to ensure that additions to TOPLEVELTYPES are done prior to any bitfield
target definitions.

cmake: Expand lists in BF generation

Uses the COMMAND_EXPAND_LISTS flag to allow for generator expressions in parameters
to GenBFCommand. As lists are now being expanded the 'args' variable must also be
quoted.

cmake: Make variables show up if previously hidden

Previously if a variable had unmet dependencies and had been hidden, by being made
an internal variable, it would not have been unhidden by the use of `option`. This
emulates the behaviour of `option` that we were wanting, but additionally using `FORCE`
to override the `INTERNAL` setting

cmake: Directly generate configuration files

Uses file(GENERATE) to directly create the contents of generated configuration files instead of
awkwardly using custom commands to echo the contents of multi line strings into files.

cmake: Invoke compilations without echo and xargs

Newer versions of cmake provide a COMMAND_EXPAND_LISTS option that allows a quoted string,
such as "a;b" to be given to a COMMAND parameter and have it expand into multiple arguments.
Using this we can much more nicely generate some of our COMMAND invocations, at the cost of
requiring a more recent cmake version

slightly more Mac friendly cmake commands

Mac has BSD sed, not GNU sed; tr seems to be more portable.

cmake: Unset CACHE variables from the CACHE

These variables were meant to be removed from the cache

cmake: Correctly set options to their DEFAULT_DISABLED values

The config_option helper was previously using cmake_dependent_option, which supposedly took
a value to set the option to in the case where it was disabled. However, this only sets
the value in the current function context, and not the cache. I do not understand why this
is the case and it seems to make that functionality completely useless. This commit simply
does the dependency checking itself and correctly sets the disabled value.

proof: Defer theory dependencies to isabelle

Instead of explicitly depending on Kernel_C.thy prior to generating proofs, this removes
the dependency check and leaves isabelle to check the dependency upon import.

Add a CMake based build system

This commit adds an alternate build system using CMake that operates indepenently of
the existing Kconfig+Kbuild+make based build system