trivial: Argc doesn't include null terminating arg

Signed-off-by: Curtis Millar <curtis@curtism.me>

Force stack order for system-V info

The order, spacing and alignment of the argv, envp, and auxv regions are
part of the system-V specification and the init in muslc uses this to
derive the location of auxv from envp.

This uses an anonymous struct to enforce the ordering and spacing of
these items in release builds such that muslc can still initialise libc.

Use internal stdint and stddef

This changes sel4runtime to use the internal minimal stdint and stddef
removing the dependency for those files from an external libc.

This also removes the imports and dependencies for stdbool, string, and
assert.

Signed-off-by: Curtis Millar <curtis@curtism.me>

trivial: style fix

Signed-off-by: Curtis Millar <curtis@curtism.me>

Move env init into external includes

This allows an external runtime to re-use the initialisation of the
runtime environment.

Signed-off-by: Curtis Millar <curtis@curtism.me>

Expose __sel4runtime_start_main

This is required for loading custom environments.

Move definitions to auxv.h

This allows the construction of other environments leveraging the
runtime.

Expose elf_helper.h in runtime interface as elf.h

This needs to be used by other libraries that need to intialise an
environment.

Update licence dates.

Use correct alignment values.

Relocate the auxv.h for sel4runtime

This will make the auxv.h for sel4runtime externally available (such as
for sel4utils).

Set sysinfo pointer.

Store more of the runtime state.

Fix indentation.

Add licenses to all files.

Word-size specific elf header file.

Rename from sel4rt to sel4runtime

Add root entry point.