Support uClibc for the tests compilations

Support uClibc for the tests compilations

There are two issues that don't allow ZFS to be compiled using uClibc.
`backtrace()`, and `program_invocation_short_name` as a `const`.
This patch adds uClibc to the conditionals in the same way there are
already for Glibc for `backtrace()`; and removes the external param
`program_invocation_short_name` because its only used here for the
whole project.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: José Luis Salvador Rufo <salvador.joseluis@gmail.com>
Closes #11600