hurd: Fix ld.so __getcwd override from libc
ld.so symbols to be overriden by libc need to be extern to really get overriden. __getcwd happens to have never been exposed, putting it to GLIBC_PRIVATE.
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ld.so symbols to be overriden by libc need to be extern to really get overriden. __getcwd happens to have never been exposed, putting it to GLIBC_PRIVATE.