fix building without optimization

It fixes two issues:
1) poldek uses the traditional GNU semantics for inline functions, not
the C99 one. Therefore builds with -00 fail with undefined references
errors.

2) _option_is_end is not exported by glibc. Builds with optimization
succeed as it is also defined as an inline function in argp.h. The patch
renders also Os-fail-workaround.patch not necessary.