Why is libtool failing here?

Question

I am installing HEALPix (c++ version) using clang and when it comes to a libtool command, the process crashes:

#  creating library /Users/keir/Software/Healpix_3.11/src/cxx/osx_clang/lib/libhealpix_cxx.a
libtool -static -o -v /Users/keir/Software/Healpix_3.11/src/cxx/osx_clang/lib/libhealpix_cxx.a
#followed by a long list of object files being archived
libtool: can't open file: /Users/keir/Software/Healpix_3.11/src/cxx/osx_clang/lib/libhealpix_cxx.a (No such file or directory)
dyld: lazy symbol binding failed: Symbol not found: _map_fd
  Referenced from: /usr/bin/libtool
  Expected in: /usr/lib/libSystem.B.dylib

dyld: Symbol not found: _map_fd
  Referenced from: /usr/bin/libtool
  Expected in: /usr/lib/libSystem.B.dylib

make[1]: *** [/Users/keir/Software/Healpix_3.11/src/cxx/osx_clang/lib/libhealpix_cxx.a] Trace/BPT trap: 5

I have searched for the meaning and resolution of this problem but there is no solution specific to the files I am using. I was wondering whether anyone could help figure this out?

I am using Xcode Version 6.1 (6A1052d) and I have up-to-date Command Line Tools - I have tried to use libtool to make a very simple archive using 2 object files and the same error comes up. I should mention that my gcc and g++ are not working and is a probable source of error - is there a way to force libtool to use clang instead (as a temporary workaround)?

My libtool version is:

Apple Computer, Inc. version cctools-590.36

Is there a more up-to-date version, perhaps?