Bug #: 4280

Bug #: 4280
Submitted by: eseidel
Reviewed by: darin
        * Scripts/build-drawtest:
        * Scripts/build-dumprendertree:
        * Scripts/build-svg2png:
        * Scripts/build-webcore-svg:
        * Scripts/build-webkit:
        * Scripts/webkitdirs.pm: added checkRequiredSystemConfig()
        Added checkRequiredSystemConfig and made all the build-* scripts
        use it to print a pretty warning when trying to compile on an
        unsupported system (less than 10.4, Xcode 2.1).
        http://bugzilla.opendarwin.org/show_bug.cgi?id=4280

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@10046 268f45cc-cd09-0410-ab3c-d52691b4dbfc