SuperBuild: patch to install properly GDAL python binding on MacOS

SuperBuild/patches/GDAL/gdal-6-pythonInstall-macx.diff

+--- gdal-2.2.1-orig/swig/python/GNUmakefile	2017-06-23 14:18:44.000000000 +0200
++++ gdal-2.2.1/swig/python/GNUmakefile	2018-03-09 18:44:06.533081541 +0100
+@@ -81,18 +81,7 @@
+ endif
+ 
+ ifdef prefix
+-    ifeq ($(shell uname),Darwin)
+-        STD_UNIX_LAYOUT=$(shell $(PYTHON) -c "from __future__ import print_function;import sys;print(\"FALSE\" if \"framework\" in sys.prefix.lower() else \"TRUE\")")
+-        ifeq ($(STD_UNIX_LAYOUT),"TRUE")
+             setup_opts+=--prefix=$(prefix)
+-        else
+-            ifdef PYTHON_INSTALL_LIB
+-                setup_opts+=--install-lib=$(PYTHON_INSTALL_LIB)
+-            endif
+-        endif
+-    else
+-        setup_opts+=--prefix=$(prefix)
+-    endif
+ endif
+ 
+ ifdef INSTALL_LAYOUT