At all times, ./configure --help provides the list of sysdeps you need to provide a --with-sysdep-* option for. As of -skalibs-2.9.3.0, there is only one sysdep in this case: +skalibs-2.14.0.0, there are two sysdeps in this case:
+libstddjb
+libskarnet
+skalibs
+Software
+skarnet.org
+
+ The following functions are declared in the skalibs/cspawn.h header, +and implemented in the libskarnet.a or libskarnet.so library. +
+ ++ cspawn is a unifier API to spawn child processes with +posix_spawn() +as a backend if supported by the system, falling back on +fork() + +execve() +otherwise. +
+ +
+ pid_t cspawn (char const *file, char const *const *argv, char const *const *envp, uint32_t flags, cspawn_fileaction const *fa, size_t n)
+Forks and execs a child as with exec_ae(file, argv, envp).
+Returns 0 if it fails, and the pid of the child if it succeeds.
+Before execing, the following operations are performed in the child:
+
+ pid_t child_spawn1_pipe (char const *file, char const *const *argv, char const *const *envp, int *fd, int w)
+Spawns file as with cspawn() with a flags value of CSPAWN_FLAGS_SIGBLOCKNONE;
+a pipe is created between the child's
+stdin (if w is 0) or stdout (if w is nonzero) and the parent.
+The parent's end of the pipe will be stored in *fd.
+
+ pid_t child_spawn1_socket (char const *file, char const *const *argv, char const *const *envp, int *fd)
+Like child_spawn1, except that a socket, not a pipe is created between the parent
+and the child. Both the child's stdin and stdout point to the socket; the parent has
+its end of the socket available in *fd.
+
+ pid_t child_spawn2 (char const *file, char const *const *argv, char const *const *envp, int *fds)
+Two pipes are created between the
+parent and the child. fds must point to an array of 2 ints: this
+array is read as well as written by child_spawn2(). On function
+call, the numbers in fds must describe what fds should be used
+in the child to contain the communication pipes (for instance, if the child
+will read from its parent on stdin and write to its parent on stdout, fds
+must contain 0 and 1). On function return, fds contains the
+descriptors for the pipes that read from / write to the child.
+
+ pid_t child_spawn3 (char const *file, char const *const *argv, char const *const *envp, int *fds)
+Three pipes are created between the
+parent and the child. fds must point to an array of 3 ints: this
+array is read as well as written by child_spawn2(). On function
+call, the numbers in fds[0] and fds[1] must describe what fds should be used
+in the child to read from (resp. write to) the parent.
+On function return, fds contains the
+descriptors for the pipes that read from / write to the child. fds[2] is
+the reading end of a pipe; the writing end is present in the child, and its number
+is available as the value of the SKALIBS_CHILD_SPAWN_FDS environment variable.
+
+ pid_t child_spawn (char const *file, char const *const *argv, char const *const *envp, int *fds, unsigned int nfds)
+More generic spawning function. fds must point to an array of at least nfds ints;
+file descriptors reading from or writing to the child will be stored there. The function returns
+0 on failure or the pid of the child on success.
+