Feature request: building musl in a portable way

[ardi <ardillasdelmonte@gmail.com>]

Hi,

Related (and as an alternative) to a previous post I made asking about
a way of isolating direct syscalls, I'm thinking about the possibility
of building musl in a way where functions that need to perform
syscalls aren't compiled, so this special compiled version of musl
would have only the functions that don't make syscalls from
themselves.

The purpose is being able to run code in system other than Linux,
replacing such functions by calls to the related functions of the
system host (provided that functions follow POSIX requirements, of
course).

Obviously, I can get this feature by modifying musl, but I'd prefer
not to modify it, because I'd like to be able to update musl to the
last version easily, and if I use a modified/customized musl version,
updating it would require merging, and possibly hard work.

If there was some way of having a switch in the build system so that
all functions that make syscalls are not compiled, I could use musl
without modifying it. Maybe the most elegant way of doing this would
be by tagging such functions with an special tag, like
"__function_makes_syscall__" or whatever. But I'm not sure.

Cheers, and thanks a lot,

ardi