[hurd] Fix unconditional use of PATH_MAX

Patch by Samuel Thibault

The GNU/Hurd system does not define an arbitrary PATH_MAX limitation, the POSIX 2001 realpath
extension can be used instead, and the size of symlinks can be determined.

Reviewed as https://reviews.llvm.org/D54677


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@351414 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed