Introduce `Library.uk`

This new file represents the first step towards proper versioning support of
external microlibrary in Unikraft.  The file itself acts as mechanism for
holding metadata-only values about the microlibrary.  This metadata is designed
to be compatible with GNU Make whilst simultaneously being human-readable and
readable by programs that are not GNU Make (e.g. tools such as KraftKit).

An important feature of this file is the inclusion of microlibrary versions.
In a later step, once relevant integrations have been made to Unikrat's core
build system and to relevant tools such as KraftKit, the user will be able to
see and select from different versions of the microlibrary.

In this initial commit, the relevant metadata is absorbed from both Makefile.uk,
Config.uk, but also includes new information such as SPDX License identifier.

Signed-off-by: Alexander Jung <alex@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Reviewed-by: Razvan Deaconescu <razvand@unikraft.io>
GitHub-Closes: #4

Correct license headers introduced by NEC Laboratories Europe GmbH

This commit removes the additional clause
"THIS HEADER MAY NOT BE EXTRACTED OR MODIFIED IN ANY WAY"
from BSD license headers that got introduced by mistake
with the following commits:
 02b28d5 - Add Makefile.uk (Charalampos Mainas)

On the one hand, this additional clause is redundant because
the BSD license already states that it must remain and the
copyright notice must be kept.
On the other hand, the clause freezes the file header
and prohibits future contributors from extending the
copyright notice for their contributions. This additional
clause is not part of the official BSD 3-clause.

The original author(s) or an authorized representative from
the author's affiliation consents to the change with a
`Reviewed-by` tag to this commit.

Signed-off-by: Simon Kuenzer <simon.kuenzer@neclab.eu>
Reviewed-by: Felipe Huici <felipe.huici@neclab.eu>
Approved-by: Razvan Deaconescu <razvan.deaconescu@cs.pub.ro>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Pull-Request: #1

Update library source url

The url for libucontext is deprecated. Update `Makefile.uk` with a valid one.

Signed-off-by: Răzvan Vîrtan <virtanrazvan@gmail.com>
Reviewed-by: Razvan Deaconescu <razvan.deaconescu@cs.pub.ro>
Approved-by: Razvan Deaconescu <razvan.deaconescu@cs.pub.ro>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Pull-Request: #3

Makefile.uk: Rename SUPPRESS_FLAGS to LIBUCONTEXT_SUPPRESS_FLAGS

Signed-off-by: Costin Lupu <costin.lupu@cs.pub.ro>
Reviewed-by: Felipe Huici <felipe.huici@neclab.eu>

Export symbols

Signed-off-by: Charalampos Mainas <Charalampos.Mainas@neclab.eu>
Reviewed-by: Costin Lupu <costin.lupu@cs.pub.ro>

Add patch for the original code

Replace signal.h with musl's ucontext.h. makecontext uses the struct
ucontext_t and this struct is defined in bits/signal.h which included
from ucontext.h. In musl signal.h includes bits/signal.h but this is not
the case with newlib which has no definition for ucontext_t struct.

Signed-off-by: Charalampos Mainas <Charalampos.Mainas@neclab.eu>
Reviewed-by: Costin Lupu <costin.lupu@cs.pub.ro>

Add Makefile.uk

Signed-off-by: Charalampos Mainas <Charalampos.Mainas@neclab.eu>
Reviewed-by: Costin Lupu <costin.lupu@cs.pub.ro>

Introduce library skeleton

We use the BSD-3-Clause license for this library glue code.

Signed-off-by: Charalampos Mainas <Charalampos.Mainas@neclab.eu>
Reviewed-by: Costin Lupu <costin.lupu@cs.pub.ro>

Initial commit (empty)