Added DIFlags in LLVMDIBuilderCreateBasicType to add optional DWARF attributes, such as DW_AT_endianity.
This change will support to add optional dwarf attributes to tag_base_type entries.
At the moment only DW_AT_endianity is supported. which is useful for bi-endian code generation such as scaler-storage-order extension in gcc
This is an extension to commit https://reviews.llvm.org/rL339714