Two small fixes for the support for SDKs on MacOSX:

1) The code that checks if an path should be located in the SDK
   explicitly excludes /usr/local. This fixes issue9046

2) The SDK variant for filtering "db_dirs_to_check" in setup.py
   was not doing anything because of a missing assignment.

Lib/distutils/unixccompiler.py

@@ -324,7 +324,9 @@ class UnixCCompiler(CCompiler):
             static = os.path.join(dir, static_f)
 
             if sys.platform == 'darwin' and (
-                    dir.startswith('/System/') or dir.startswith('/usr/')):
+                dir.startswith('/System/') or (
+                dir.startswith('/usr/') and not dir.startswith('/usr/local/'))):
+
                 shared = os.path.join(sysroot, dir[1:], shared_f)
                 dylib = os.path.join(sysroot, dir[1:], dylib_f)
                 static = os.path.join(sysroot, dir[1:], static_f)

setup.py

@@ -47,7 +47,7 @@ def is_macosx_sdk_path(path):
     """
     Returns True if 'path' can be located in an OSX SDK
     """
-    return path.startswith('/usr/') or path.startswith('/System/')
+    return (path.startswith('/usr/') and not path.startswith('/usr/local')) or path.startswith('/System/')
 
 def find_file(filename, std_dirs, paths):
     """Searches for the directory where a given file is located,
@@ -922,6 +922,7 @@ class PyBuildExt(build_ext):
                         else:
                             if os.path.isdir(dn):
                                 tmp.append(dn)
+                    db_dirs_to_check = tmp
 
                 # Look for a version specific db-X.Y before an ambiguoius dbX
                 # XXX should we -ever- look for a dbX name?  Do any