#i114728# allow OSX platform SDKs that support OSX 10.7

Some newer Mac SDKs are backward compatible with an OSX 10.7 deployment target.
Allowing the build with such compatible SDKs enables the use of plain XCode,
even when XCode>=5 dropped the 10.7 SDK.

configure.in

@@ -937,10 +937,6 @@ AC_ARG_WITH(rat-scan,
                           a separately installed library.
 ],with_rat_scan=$withval,)
 
-AC_ARG_WITH(macosx-sdk-version,
-[  --with-macosx-sdk-version=<version>   Specify the MacOSX platform SDK version, default is 10.7. Only 10.7 or higher is supported.
-],,)
-
 BUILD_TYPE="OOo"
 ADDITIONAL_REPOSITORIES="../ext_libraries"
 SCPDEFS=""
@@ -3911,32 +3907,32 @@ AC_SUBST(LIBXML_LIBS)
 
 
 dnl ===================================================================
-dnl Checks for MacOS platform SDK. Default is 10.7
+dnl Checks for a MacOS platform SDK which supports a OSX 10.7 deployment target
 dnl ===================================================================
 if test  "$_os" = "Darwin"; then
-   AC_MSG_CHECKING([checking MacOS platform SDK])
-   sdk_version=10.7
+   sdk_target=10.7
+   AC_MSG_CHECKING([checking SDK compatiblity with OSX $sdk_target])
 
-   if test -n "$with_macosx_sdk_version"; then
-      sdk_version=$with_macosx_sdk_version
-   fi
-
-   sdk_minor=`echo $sdk_version | cut -d"." -f2`
+   sdk_minor=`echo $sdk_target | cut -d"." -f2`
 
    if test "$sdk_minor" -lt "7"; then
       AC_MSG_ERROR([SDK version < 10.7 is not longer supported])
    else
       AC_MSG_RESULT([yes])
-      if test "$sdk_minor" -ge "7"; then
-          MACOSX_DEPLOYMENT_TARGET=$sdk_version
+      MACOSX_DEPLOYMENT_TARGET=$sdk_target
+
+      AC_MSG_CHECKING([for SDKs compatible with $MACOSX_DEPLOYMENT_TARGET])
+      sdk_found=`xcodebuild -showsdks | grep "sdk macosx10.[[789]]" | sed -e "s/.*sdk //" | head -n1`
+      if test -z "$sdk_found"; then
+         AC_MSG_ERROR([No SDK with OSX $sdk_target compatibility found])
       fi
 
-      sdk_path=`xcodebuild -version -sdk macosx$MACOSX_DEPLOYMENT_TARGET Path`
+      sdk_path=`xcodebuild -version -sdk ${sdk_found} Path`
       AC_MSG_CHECKING([for $sdk_path])
       if test -d "$sdk_path"; then
          AC_MSG_RESULT([yes])
       else
-         AC_MSG_ERROR([No proper MacOS platform SDK, not found])
+         AC_MSG_ERROR([MacOS SDK $sdk_found is not available at $sdk_path])
       fi
 
       MACOSX_SDK_PATH=$sdk_path