Do not detect Xcode and set -isysroot for its SDK, since that messes up
our toolchain, and hence makes any compilation fail, bug #445308

--- Modules/Platform/Darwin.cmake
+++ Modules/Platform/Darwin.cmake
@@ -60,18 +60,18 @@
 endif()
 
 # Ask xcode-select where to find /Developer or fall back to ancient location.
-execute_process(COMMAND xcode-select -print-path
-  OUTPUT_VARIABLE _stdout
-  OUTPUT_STRIP_TRAILING_WHITESPACE
-  ERROR_VARIABLE _stderr
-  RESULT_VARIABLE _failed)
-if(NOT _failed AND IS_DIRECTORY ${_stdout})
-  set(OSX_DEVELOPER_ROOT ${_stdout})
-elseif(IS_DIRECTORY "/Developer")
-  set(OSX_DEVELOPER_ROOT "/Developer")
-else()
+#execute_process(COMMAND xcode-select -print-path
+#  OUTPUT_VARIABLE _stdout
+#  OUTPUT_STRIP_TRAILING_WHITESPACE
+#  ERROR_VARIABLE _stderr
+#  RESULT_VARIABLE _failed)
+#if(NOT _failed AND IS_DIRECTORY ${_stdout})
+#  set(OSX_DEVELOPER_ROOT ${_stdout})
+#elseif(IS_DIRECTORY "/Developer")
+#  set(OSX_DEVELOPER_ROOT "/Developer")
+#else()
   set(OSX_DEVELOPER_ROOT "")
-endif()
+#endif()
 
 execute_process(COMMAND sw_vers -productVersion
   OUTPUT_VARIABLE CURRENT_OSX_VERSION
@@ -91,10 +91,10 @@
 # CMAKE_OSX_DEPLOYMENT_TARGET
 
 # Set cache variable - end user may change this during ccmake or cmake-gui configure.
-if(_CURRENT_OSX_VERSION VERSION_GREATER 10.3)
-  set(CMAKE_OSX_DEPLOYMENT_TARGET "$ENV{MACOSX_DEPLOYMENT_TARGET}" CACHE STRING
-    "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value.")
-endif()
+#if(_CURRENT_OSX_VERSION VERSION_GREATER 10.3)
+#  set(CMAKE_OSX_DEPLOYMENT_TARGET "$ENV{MACOSX_DEPLOYMENT_TARGET}" CACHE STRING
+#    "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value.")
+#endif()
 
 #----------------------------------------------------------------------------
 # CMAKE_OSX_SYSROOT