[dsymutil] Generate debug_aranges section.

[dsymutil] Generate debug_aranges section.

This actually shares most of its implementation with the  generation
of the debug_ranges (the absence of 'a' is not a typo) contribution
for the unit's DW_AT_ranges attribute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232246 91177308-0d34-0410-b5e6-96231b3b80d8