This addresses point 1 of PR44213. (https://bugs.llvm.org/show_bug.cgi?id=44213).
The DW_AT_LLVM_sysroot attribute is used for Clang module debug info, to allow LLDB to import a Clang module from source. Currently it is part of each DW_TAG_module, however, it is the same for all modules in a compile unit. It is more efficient and less ambiguous to store it once in the DW_TAG_compile_unit.
This should have no effect on DWARF consumers other than LLDB.
indentation seems of?