crunchgen: remove -dc from linker invocation

In GNU ld and ld.lld, -dc is used with -r to allocate space to COMMON
symbols.  It is presumably to work around legacy code which cannot
handle COMMON symbols in relocatable output.  ld.lld may remove -dc or
make it a no-op for the 15.0.0 release.

As of 7420b323a0 crunch/crunchide does not require -dc, as the symbol
hiding technique no longer relied on making symbols local.

In addition -fno-common is now the default in Clang and GCC, so -dc
serves no purpose as the compiler does not generate COMMON symbols
anyway.

See https://maskray.me/blog/2022-02-06-all-about-common-symbols for more
detail on common symbols.

Reviewed by:	emaste
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D34215

usr.sbin/crunch/crunchgen/crunchgen.c

@@ -1123,7 +1123,7 @@ prog_makefile_rules(FILE *outmk, prog_t *p)
 		fprintf(outmk, " $(%s_LIBS)", p->ident);
 
 	fprintf(outmk, "\n");
-	fprintf(outmk, "\t$(CC) -nostdlib -Wl,-dc -r -o %s.lo %s_stub.o $(%s_OBJPATHS)",
+	fprintf(outmk, "\t$(CC) -nostdlib -r -o %s.lo %s_stub.o $(%s_OBJPATHS)",
 	    p->name, p->name, p->ident);
 	if (p->libs)
 		fprintf(outmk, " $(%s_LIBS)", p->ident);

usr.sbin/crunch/crunchide/crunchide.c

@@ -28,9 +28,7 @@
 /*
  * crunchide.c - tiptoes through a symbol table, hiding all defined
  *	global symbols.  Allows the user to supply a "keep list" of symbols
- *	that are not to be hidden.  This program relies on the use of the
- * 	linker's -dc flag to actually put global bss data into the file's
- * 	bss segment (rather than leaving it as undefined "common" data).
+ *	that are not to be hidden.
  *
  * 	The point of all this is to allow multiple programs to be linked
  *	together without getting multiple-defined errors.
@@ -40,7 +38,7 @@
  *	    int foo_main(int argc, char **argv){ return main(argc, argv); }
  *      like so:
  *	    cc -c foo.c foostub.c
- *	    ld -dc -r foo.o foostub.o -o foo.combined.o
+ *	    ld -r foo.o foostub.o -o foo.combined.o
  *	    crunchide -k _foo_main foo.combined.o
  *	at this point, foo.combined.o can be linked with another program
  * 	and invoked with "foo_main(argc, argv)".  foo's main() and any