[vbox-dev] Fix build on OS X 10.10 (bug #13693)

[Daniel Cotton]

MIT Licensed.

Index: configure
===================================================================
--- configure   (revision 53543)
+++ configure   (working copy)
@@ -2145,7 +2145,7 @@
   darwin_ver=`uname -r`
   case "$darwin_ver" in
     14\.*)
-      check_xcode_sdk_path "$WITH_XCODE_SDK_DIR"
+      check_xcode_sdk_path "$WITH_XCODE_DIR"
       [ $? -eq 1 ] || fail
       darwin_ver="10.10" # Yosemite
       sdk=$WITH_XCODE_DIR/Developer/SDKs/MacOSX10.6.sdk