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

--- cmake-3.16.5/Modules/Platform/Darwin-Initialize.cmake	2020-03-04 07:50:44.000000000 -0600
+++ cmake-3.16.5/Modules/Platform/Darwin-Initialize.cmake.update	2020-11-26 19:18:28.000000000 -0600
@@ -1,16 +1,16 @@
 # 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
@@ -34,10 +34,10 @@
 # CMAKE_OSX_DEPLOYMENT_TARGET
 
 # Set cache variable - end user may change this during ccmake or cmake-gui configure.
-if(CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND _CURRENT_OSX_VERSION VERSION_GREATER 10.3)
-  set(CMAKE_OSX_DEPLOYMENT_TARGET "$ENV{MACOSX_DEPLOYMENT_TARGET}" CACHE STRING
-    "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value.")
-endif()
+#if(CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND _CURRENT_OSX_VERSION VERSION_GREATER 10.3)
+#  set(CMAKE_OSX_DEPLOYMENT_TARGET "$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