With lld 14 and no additional LDFLAGS the referenced foo()-function
was optimized out, as an executable was compiled with no reference
to the function, also removing the undefined references to the tested
libc functions.

This caused the sysdep mechanism to misdetect hasutmploginlogout.h-yes.c
and sysdep/hasutmplogwtmp.h-yes.c on musl libc as true, while it should
be false, which broke the build later on on the real references in
tinyssh code.

This can also be reproduced with gcc with CFLAGS=-ffunction-sections
and LDFLAGS=-Wl,--gc-sections.

Instead reference them, but do not evaluate them at runtime by making
the prequisite argc == 0. This should be safe from being optimized out
even with LTO.