Freestanding OCaml runtime

This package builds a freestanding OCaml runtime suitable for linking with a unikernel base layer (currently only Solo5 is supported).

The following components are installed:

In PREFIX/lib/ocaml-freestanding:

• libnolibc.a: libc interfaces required by OCaml runtime.
• libopenlibm.a: libm required by OCaml runtime.
• libasmrun.a, libotherlibs.a: OCaml native code runtime.

In PREFIX/include/ocaml-freestanding/include:

• Header files for nolibc and openlibm.

In PREFIX/include/ocaml-freestanding/include/caml:

• Header files for OCaml runtime.

Downstream packages should use pkg-config --cflags ocaml-freestanding when compiling C code using these components and pkg-config --libs ocaml-freestanding during the link step.

Tested against OCaml 4.02.3 and 4.03.0. Other versions will require changing configure.sh.

Assuming your unikernel base layer is packaged for OPAM in a similar fashion to Solo5 this should be as simple as:

1. Adding the appropriate clauses to determine the OPAM packages required and FREESTANDING_CFLAGS for compilation to configure.sh.
2. Implementing a nolibc/sysdeps_yourkernel.c.

Note that the nolibc code is intentionally strict about namespacing of APIs and header files. If your base layer exports symbols or defines types which conflict with nolibc then the recommended course of action is to fix your base layer to not export anything defined by "POSIX" or "standard C".