RZ succeeds if x is zero, and fails if x is nonzero, treating a
nonzero value as a error number as in errno(3) to print the message.
The following library routines instead return -1 on failure and set
errno to the error code:
fuse_opt_add_arg
fuse_opt_add_opt
fuse_opt_add_opt_escaped
fuse_opt_insert_arg
lseek
system
So use RL instead for those -- succeeds if x is zero, and fails if x
is -1.
This shouldn't make any tests newly fail or newly succeed -- the
functions in question only ever return 0 or -1 -- but if the tests
were already failing anywhere, they will now fail with meaningful
messages.
TBD: dlinfo, which isn't fit for RL or RZ since it reports errors via
dlerror() rather than errno.