I suggest to do this change, together with D35987 it allows to detemplate code like:
for (elf::ObjectFile<ELFT> *File : Symtab<ELFT>::X->getObjectFiles()) {
for (SymbolBody *Body : File->getSymbols()) {
auto *D = dyn_cast<DefinedRegular>(Body);
if (!D || !D->Section)
continue;Going to use it in D35843, which need iterating over DefinedRegular symbols
from non-ELFT-templated code.
Patch detemplates finalizeShtGroup() to show it is itself can be useful for detemplation.