Align global strings according to data layout

When creating global strings, some targets have requirements that need to
be taken into account. Previously, the global strings created by
`IRBuilder::createGlobalString` had a hard-coded alignment of `1`.

This commit makes it so that the alignment is taken from the data layout
instead, giving targets the chance to align global strings according to
their preferences.

Author: dominik-steenken

llvm/lib/IR/IRBuilder.cpp

@@ -52,7 +52,7 @@ GlobalVariable *IRBuilderBase::CreateGlobalString(StringRef Str,
       *M, StrConstant->getType(), true, GlobalValue::PrivateLinkage,
       StrConstant, Name, nullptr, GlobalVariable::NotThreadLocal, AddressSpace);
   GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
-  GV->setAlignment(Align(1));
+  GV->setAlignment(M->getDataLayout().getPreferredAlign(GV));
   return GV;
 }