OSX Makefile Build Bug Fix

Solution to this problem: http://forum.openframeworks.cc/index.php/topic,13235.msg56894.html

Since config.osx.default.mk only looks for the latest SDK version installed, the version may not match the current OSX. In order to get current OSX version instead of the latest SDK version, I changed config.osx.default.mk as

diff --git a/libs/openFrameworksCompiled/project/osx/config.osx.default.mk b/libs/openFrameworksCompiled/project/osx/config.osx.default.mk
index ad4c5bb..d05f69b 100644
--- a/libs/openFrameworksCompiled/project/osx/config.osx.default.mk
+++ b/libs/openFrameworksCompiled/project/osx/config.osx.default.mk
@@ -90,13 +90,7 @@ endif
 #endif

 ifndef MAC_OS_SDK
-    ifeq ($(wildcard $(MAC_OS_SDK_PATH)/MacOSX10.8.sdk),$(MAC_OS_SDK_PATH)/MacOSX10.8.sdk)
-               MAC_OS_SDK=10.8
-       else ifeq ($(wildcard $(MAC_OS_SDK_PATH)/MacOSX10.7.sdk),$(MAC_OS_SDK_PATH)/MacOSX10.7.sdk)
-               MAC_OS_SDK=10.7
-       else ifeq ($(wildcard $(MAC_OS_SDK_PATH)/MacOSX10.6.sdk),$(MAC_OS_SDK_PATH)/MacOSX10.6.sdk)
-               MAC_OS_SDK=10.6
-       endif
+    MAC_OS_SDK=$(shell sw_vers -productVersion | cut -f1,2 -d.)
 endif

 MAC_OS_SDK_ROOT = $(MAC_OS_SDK_PATH)/MacOSX$(MAC_OS_SDK).sdk

It worked on my 10.7.5 machine, whose latest SDK version is 10.8.

Start with libs/openFrameworksCompiled/project/osx/config.osx.default.mk and inspect how MAC_OS_SDK and MAC_OS_SDK_ROOT are selected. Verify that the build chooses the current macOS version rather than only the newest installed SDK, including the 10.7.5 case described in the issue.