crunchgen: don't pass -dc to the linker

[emaste]

Summary

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.

Test Plan

• apply this change
• modify Makefile.inc1 to make crunchide an unconditional build tool (to be replaced with __FreeBSD_version test before commit)
• build rescue
• ad-hoc sanity test result

[pfg]

Looks OK.

[emaste]

As it turns out this was based on an old experiment with lld. lld currently accepts (and ignores) -dc, as it always converts common symbols into allocated .bss symbols, so this change is unnecessary.

All else being equal I'll just drop the change and avoid possible unintended consequences.