[Debuginfod] Fix warnings
This patch fixes:
llvm/lib/Debuginfod/Debuginfod.cpp:592:12: error: moving a local
object in a return statement prevents copy elision
[-Werror,-Wpessimizing-move]
llvm/lib/Debuginfod/Debuginfod.cpp:613:12: error: moving a local
object in a return statement prevents copy elision
[-Werror,-Wpessimizing-move]
