In the `_osx_support.py` module, there seems to be a bug in the method `compiler_fixup` which occurs if 

* the `customize_compiler` method from `distutils/sysconfig` has been called and after that
* `_compile` from `distutils/unixcompiler.py` is called. The `_compile` method uses `_osx_support.compiler_fixup`.

The critical line in compiler_fixup is:

`compiler_so = list(compiler_so)`.

Usually `compiler_so` is a list like `['cc']` but not when `customize_compiler` (from sysconfig) has been called. The value returned by `sysconfig.get_config_var('LDSHARED')` is a unicode like for example in the case of a Python 2.7.5 built via Homebrew: 
  
    "cc -bundle -undefined dynamic_lookup -L/homebrew/lib -L/homebrew/opt/sqlite/lib -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk".
When `list()` is applied to the value, it is split at each character and that cannot be intended.

I am not sure if I fully understand, but to fix this in `compiler_fixup`, instead of `compiler_so = list(compiler_so)`, I'd propose something along the lines of:

    if isinstance(compiler_so, (str,unicode)):
        compiler_so = compiler_so.split()

I found this by trying to `pip install cython` (it uses customize_compiler, I guess) on a homebrewed python.

To reproduce in an interactive shell we can emulate what is going on by calling `compiler_fixup` directly with the values sysconfig has stored. The exact string does not matter, because I think the any value returned by `sysconfig_get_config_var` is a (unicode) string and not a list:

    import sysconfig
    import _osx_support
    _osx_support.compiler_fixup(sysconfig.get_config_var('LDSHARED'),sysconfig.get_config_var('CFLAGS'))


Not sure if other python versions are affected. I wasn't aware of `_osx_support` at all until now.