The string literal "stack frame size" passed to the base class
constructor created a temporary Twine that was destroyed after
the base constructor completed, leaving a dangling reference.
Fix by storing the Twine as a member variable in the derived class,
ensuring it lives as long as the diagnostic object itself.
Fixes ASAN stack-use-after-scope error in
Clang :: Misc/backend-stack-frame-diagnostics-fallback.cpp
LLVM :: CodeGen/X86/2007-04-24-Huge-Stack.ll
LLVM :: CodeGen/X86/huge-stack-offset.ll
LLVM :: CodeGen/X86/huge-stack-offset2.ll
LLVM :: CodeGen/X86/huge-stack.ll
LLVM :: CodeGen/X86/large-displacements.ll
LLVM :: CodeGen/X86/stack-clash-extra-huge.ll
LLVM :: CodeGen/X86/warn-stack.ll
LLVM :: CodeGen/X86/win64-stackprobe-overflow.ll
ee405335f0