[lldb] Add support for recognizing swift ast sections in object files

In Apple's downstream fork, there is support for understanding the swift
AST sections in various binaries. Even though the lldb on llvm.org does
not have support for debugging swift, I think it makes sense to move
support for recognizing swift ast sections upstream.

Differential Revision: https://reviews.llvm.org/D159142

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

@@ -1009,6 +1009,7 @@ SectionType ObjectFilePECOFF::GetSectionType(llvm::StringRef sect_name,
           // .eh_frame can be truncated to 8 chars.
           .Cases(".eh_frame", ".eh_fram", eSectionTypeEHFrame)
           .Case(".gosymtab", eSectionTypeGoSymtab)
+          .Case("swiftast", eSectionTypeSwiftModules)
           .Default(eSectionTypeInvalid);
   if (section_type != eSectionTypeInvalid)
     return section_type;