hi in running nix on OSX, im having troubles compiling elixir deps from my nix-shell.
`CoreServices/CoreServices.h' file not found`

The clang/xcode wrapper is quite out of date...

if i manualy try to compile the thing with system instead of nix/store clang (`/usr/bin/clang`) it works fine
```
[nix]⋊> ~/r/e/r/d/file_system on master ⨯ /usr/bin/clang -framework CoreFoundation -framework CoreServices -Wno-deprecated-declarations c_src/mac/*.c -o priv/mac_listener                          22:55:16
[nix]⋊> ~/r/e/r/d/file_system on master ⨯ which clang                                                                                                                                               22:55:22
/nix/store/8b0gj3bmcy5bh1zcnhn0146199b3m5kb-clang-wrapper-5.0.1/bin/clang
[nix]⋊> ~/r/e/r/d/file_system on master ⨯ clang -framework CoreFoundation -framework CoreServices -Wno-deprecated-declarations c_src/mac/*.c -o priv/mac_listener                                   22:56:31
In file included from c_src/mac/cli.c:2:
In file included from c_src/mac/cli.h:4:
c_src/mac/common.h:5:10: fatal error: 'CoreServices/CoreServices.h' file not found
#include <CoreServices/CoreServices.h>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
```