Add support for C++ runtime

[jmi-reds]

Add the support of C++ runtime to SO3.

The MUSL toolchain for C++ will be used

[jmi-reds]

With simple Hello-World C++, the following syscall are missing:

• set_tid_address
• mmap - MAP_ANONYMOUS case
• writev
• exit_group

The needed syscall will be added in issue #144

[jmi-reds]

The support of musl and the missing syscall were added with #144.

The following of support of C++ is now done in issue #236.