```
lang=bash
$ ../arcanist/bin/arc liberate
```
from one extension dir produces
```
counterexample
[2015-08-20 10:26:26] EXCEPTION: (Exception) xhpast is broken. at [<phutil>/src/parser/xhpast/bin/PhutilXHPASTBinary.php:47]
phutil(head=master, ref.master=e509fc30ae78)
#0 PhutilXHPASTBinary::build() called at [<phutil>/src/moduleutils/PhutilLibraryMapBuilder.php:446]
#1 PhutilLibraryMapBuilder::analyzeLibrary() called at [<phutil>/src/moduleutils/PhutilLibraryMapBuilder.php:77]
#2 PhutilLibraryMapBuilder::buildMap() called at [<phutil>/src/moduleutils/PhutilLibraryMapBuilder.php:109]
#3 PhutilLibraryMapBuilder::buildAndWriteMap() called at [<phutil>/scripts/phutil_rebuild_map.php:75]
zsh: exit 255 ../arcanist/bin/arc liberate
```