[gn build] Port 94206c9

Author: llvmgnsyncbot

llvm/utils/gn/secondary/lldb/source/Plugins/SymbolFile/DWARF/BUILD.gn

@@ -64,6 +64,7 @@ static_library("DWARF") {
     "DebugNamesDWARFIndex.cpp",
     "LogChannelDWARF.cpp",
     "ManualDWARFIndex.cpp",
+    "ManualDWARFIndexSet.cpp",
     "NameToDIE.cpp",
     "SymbolFileDWARF.cpp",
     "SymbolFileDWARFDebugMap.cpp",