Updated the Build file to clean the .wyil and .class files from the stdlib directory.
Updated the Build file to clean the .wyil and .class files from the stdlib directory.

hjwylde/whiley-compiler,hjwylde/whiley-compiler,hjwylde/whiley-compiler,hjwylde/whiley-compiler,hjwylde/whiley-compiler,Whiley/WhileyCompiler