The linker's -dc option converts common symbols into regular, allocated .bss symbols. However, this is not required by the crunch build process or rescue, and LLVM's lld linker does not support the -dc option. These symbols will be converted into allocated .bss symbols by the final binary link. If desired we can restore the previous (no common syms) configuration by adding -fno-common to the crunchgen-provided CFLAGS.
Note: we would see a difference in behaviour if the same common symbol exists in two object files: previously it would result in a multiple definition link error, now the common symbols will be combined.