fixing minor typo in path for runing make

Micro-Python-on-Mac-OSX.md

@@ -19,7 +19,7 @@ In order to compile on OSX you will need the following software packages install
 * If you like using git completion or `$(__git_ps1)` for your prompt, then add the following line to your ~/.bashrc file: `. /opt/local/share/git/contrib/completion/git-prompt.sh`
 
 ## Build Process
-Same as on Linux - go to `micropython/unix` and run `make` (or `make -B` or `make clean; make` if rebuilding.
+Same as on Linux - go to `micropython/ports/unix` and run `make` (or `make -B` or `make clean; make` if rebuilding.
 
 If installing libffi with homebrew, you might have to specify its location to pkgconfig
 ```