simplify and fix getcwd
simplify and fix getcwd

The fallback code is not used as all supported kernels have the
syscall. Check if a absolute path is returned from syscall.

wbx-github/uclibc-ng,kraj/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng