XCode updates on MacOS requires a full rebuild

[johnoel]

For any update to the XCode minor version will cause a need recompile admb. Currently, the build and script files will check if the clang version has clang-1100. For XCode update 11.4, the version was updated to clang-1103. Since it is different from clang-1100, the build files require a rebuild to rename the libraries. To fix this only check for major version clang-11 which in binary compatible with all minor version of XCode 11.*.