Update contents of darwinbuild.xcconfig

This will no longer produce spurious warnings in Xcode
(caused by the use of the now-broken ADDITIONAL_SDKS
build setting), as well as greatly simplify the process
used to locate the installed roots.

darwinbuild/darwinbuild.in

@@ -649,17 +649,8 @@ if [ "$noload" != "YES" ]; then
 		cat <<EOF > $REAL_SRCROOT/darwinbuild.xcconfig
 DEPROOT = $REAL_DEPROOT
 
-ADDITIONAL_SDKS = \$(DEPROOT)
-SYSTEM_HEADER_SEARCH_PATHS_USER = \$(DEPROOT)/System/Library/Frameworks/System.framework/PrivateHeaders \$(DEPROOT)/usr/include \$(DEPROOT)/usr/local/include
-SYSTEM_HEADER_SEARCH_PATHS_KERNEL = \$(DEPROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders \$(DEPROOT)/System/Library/Frameworks/Kernel.framework/Headers
-FRAMEWORK_SEARCH_PATHS_USER = \$(DEPROOT)/System/Library/Frameworks \$(DEPROOT)/System/Library/PrivateFrameworks
-
-// Default to user-mode unless \$(DARWINBUILD_SDK_MODE) is set to "KERNEL".
-SYSTEM_HEADER_SEARCH_PATHS_ = \$(SYSTEM_HEADER_SEARCH_PATHS_USER)
-FRAMEWORK_SEARCH_PATHS_ = \$(FRAMEWORK_SEARCH_PATHS_USER)
-
-SYSTEM_HEADER_SEARCH_PATHS = \$(SYSTEM_HEADER_SEARCH_PATHS_\$(DARWINBUILD_SDK_MODE)) \$(inherited)
-FRAMEWORK_SEARCH_PATHS = \$(FRAMEWORK_SEARCH_PATHS_\$(DARWINBUILD_SDK_MODE)) \$(inherited)
+SYSTEM_HEADER_SEARCH_PATHS = \$(DEPROOT)/System/Library/Frameworks/System.framework/PrivateHeaders \$(DEPROOT)/usr/include \$(DEPROOT)/usr/local/include
+FRAMEWORK_SEARCH_PATHS = \$(DEPROOT)/System/Library/Frameworks \$(DEPROOT)/System/Library/PrivateFrameworks
 EOF
 
 		echo
@@ -770,17 +761,8 @@ fi
 cat <<EOF > $REAL_SRCROOT/darwinbuild.xcconfig
 DEPROOT = $DEPROOT
 
-ADDITIONAL_SDKS = \$(DEPROOT)
-SYSTEM_HEADER_SEARCH_PATHS_USER = \$(DEPROOT)/System/Library/Frameworks/System.framework/PrivateHeaders \$(DEPROOT)/usr/include \$(DEPROOT)/usr/local/include
-SYSTEM_HEADER_SEARCH_PATHS_KERNEL = \$(DEPROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders \$(DEPROOT)/System/Library/Frameworks/Kernel.framework/Headers
-FRAMEWORK_SEARCH_PATHS_USER = \$(DEPROOT)/System/Library/Frameworks \$(DEPROOT)/System/Library/PrivateFrameworks
-
-// Default to user-mode unless \$(DARWINBUILD_SDK_MODE) is set to "KERNEL".
-SYSTEM_HEADER_SEARCH_PATHS_ = \$(SYSTEM_HEADER_SEARCH_PATHS_USER)
-FRAMEWORK_SEARCH_PATHS_ = \$(FRAMEWORK_SEARCH_PATHS_USER)
-
-SYSTEM_HEADER_SEARCH_PATHS = \$(SYSTEM_HEADER_SEARCH_PATHS_\$(DARWINBUILD_SDK_MODE)) \$(inherited)
-FRAMEWORK_SEARCH_PATHS = \$(FRAMEWORK_SEARCH_PATHS_\$(DARWINBUILD_SDK_MODE)) \$(inherited)
+SYSTEM_HEADER_SEARCH_PATHS = \$(DEPROOT)/System/Library/Frameworks/System.framework/PrivateHeaders \$(DEPROOT)/usr/include \$(DEPROOT)/usr/local/include
+FRAMEWORK_SEARCH_PATHS = \$(DEPROOT)/System/Library/Frameworks \$(DEPROOT)/System/Library/PrivateFrameworks
 EOF
 
 ###