* guix/build/syscalls.scm (kernel?, processes): New procedures.
* guix/build/syscalls.scm, tests/syscalls.scm: New files. * Makefile.am (MODULES): Add guix/build/syscalls.scm. (SCM_TESTS): Add tests/syscalls.scm. * guix/utils.scm (%libc-errno-pointer, errno): Remove; take from (guix build syscalls).