Add identical COMDAT folding using a color-refinement over foldable
read-only sections. Hash section contents, relocation targets, and target
colors until partitions stabilize, then redirect folded COMDAT symlinks
and discard duplicate sections.
Honor .llvm_addrsig via /LLVM_ADDRSIG so address-significant sections
are not folded, keep separate color space for code, unwind info, and
MSVC vftables, and update COMDAT symbol/section mapping after folding.
Add linker tests covering function folding, relocation-sensitive folds,
alignment, color-space separation, symlink chains, .llvm_addrsig,
pdata/xdata, and C++ ICF cases.
Nikita Smith
d34e1a7802