### Please describe the problem.
git-annex doesn't start.

### What steps will reproduce the problem?
launch git-annex from terminal (if it is ran from GUI it doesn't open without notifying any error)

### What version of git-annex are you using? On what operating system?
Version: 6.20171128-g58b04cd2e on OS X 10.13.1 (17B1003)

### Please provide any additional information below.
I solved the issue by manually changing the file /Applications/git-annex.app/Contents/MacOS/bundle/B which is an alias pointing to the file /Applications/git-annex.app/Contents/MacOS/bundle/usr/lib/libz.1.dylib with a new alias having the same name 'B' which link to /usr/lib/libz.1.dylb.
I'm pretty sure this is not an optimal and general solution, but it is useful in order to prove what's the problem. Further, for it worked. 

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log
dyld: Symbol not found: _inflateValidate
  Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/Resources/libPng.dylib
  Expected in: /Applications/git-annex.app/Contents/MacOS/bundle/B
 in /System/Library/Frameworks/ImageIO.framework/Versions/A/Resources/libPng.dylib
Abort trap: 6

# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

> OSX autobuild is updated and no longer contains the copy of libz.
> [[done]]
