Revert "removes parallel build form macos port."

This reverts commit 232daff.

Author: kdschlosser

builder/macOS.py

@@ -15,12 +15,6 @@
 from . import unix
 from . import spawn
 
-unix.unix_cmd = [
-    'make',
-    '',
-    '',
-    '-C',
-]
 
 unix.REAL_PORT = 'macOS'
 
@@ -33,8 +27,6 @@ def parse_args(extra_args, lv_cflags, board):
 
 
 def build_commands(not_sure, extra_args, script_dir, lv_cflags, board):
-
-
     return _build_commands(not_sure, extra_args, script_dir, lv_cflags, board)