Update Git ignore to ignore downloaded LLVM builds.
Update Git ignore to ignore downloaded LLVM builds.

mono/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,ddobrev/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,ddobrev/CppSharp,mono/CppSharp,zillemarco/CppSharp,zillemarco/CppSharp,mono/CppSharp,mono/CppSharp,mono/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,mono/CppSharp