Index: cmake/Modules/CompilerRTDarwinUtils.cmake
===================================================================
--- cmake/Modules/CompilerRTDarwinUtils.cmake
+++ cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -1,9 +1,15 @@
 include(CMakeParseArguments)
 
+set(DARWIN_${sdk_name}_CACHED_SYSROOT "" CACHE STRING "Darwin SDK path for SDK ${sdk_name}.")
+
 # On OS X SDKs can be installed anywhere on the base system and xcode-select can
 # set the default Xcode to use. This function finds the SDKs that are present in
 # the current Xcode.
-function(find_darwin_sdk_dir var sdk_name)
+function(find_darwin_sdk_dir var sdk_name)  
+  if(DARWIN_${sdk_name}_CACHED_SYSROOT)
+    set(${var} ${DARWIN_${sdk_name}_CACHED_SYSROOT} PARENT_SCOPE)
+    return()
+  endif()
   # Let's first try the internal SDK, otherwise use the public SDK.
   execute_process(
     COMMAND xcodebuild -version -sdk ${sdk_name}.internal Path
@@ -26,6 +32,7 @@
   if(result_process EQUAL 0)
     set(${var} ${var_internal} PARENT_SCOPE)
   endif()
+  set(DARWIN_${sdk_name}_CACHED_SYSROOT ${var_internal} CACHE STRING "Darwin SDK path for SDK ${sdk_name}." FORCE)
 endfunction()
 
 # There isn't a clear mapping of what architectures are supported with a given