[dev.link] cmd/link: remove Flag8 from amd64

It's only ever checked for plan 9 and it was irrelevantly set.

Change-Id: I225d4be645f573ceccde47ec2236bf3dbeb0ea70
Reviewed-on: https://go-review.googlesource.com/c/go/+/234886
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/link/internal/amd64/asm.go

@@ -690,16 +690,12 @@ func asmb2(ctxt *ld.Link, _ *loader.Loader) {
 		fallthrough
 
 	case objabi.Hplan9:
-		break
-
 	case objabi.Hlinux,
 		objabi.Hfreebsd,
 		objabi.Hnetbsd,
 		objabi.Hopenbsd,
 		objabi.Hdragonfly,
 		objabi.Hsolaris:
-		ld.Flag8 = true /* 64-bit addresses */
-
 	case objabi.Hwindows:
 		break
 	}

src/cmd/link/internal/ld/main.go

@@ -84,7 +84,7 @@ var (
 	FlagS           = flag.Bool("s", false, "disable symbol table")
 	flagU           = flag.Bool("u", false, "reject unsafe packages")
 	FlagW           = flag.Bool("w", false, "disable DWARF generation")
-	Flag8           bool // use 64-bit addresses in symbol table
+	flag8           bool // use 64-bit addresses in symbol table
 	flagInterpreter = flag.String("I", "", "use `linker` as ELF dynamic linker")
 	FlagDebugTramp  = flag.Int("debugtramp", 0, "debug trampolines")
 	FlagStrictDups  = flag.Int("strictdups", 0, "sanity check duplicate symbol contents during object file reading (1=warn 2=err).")
@@ -121,7 +121,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 
 	// TODO(matloob): define these above and then check flag values here
 	if ctxt.Arch.Family == sys.AMD64 && objabi.GOOS == "plan9" {
-		flag.BoolVar(&Flag8, "8", false, "use 64-bit addresses in symbol table")
+		flag.BoolVar(&flag8, "8", false, "use 64-bit addresses in symbol table")
 	}
 	flagHeadType := flag.String("H", "", "set header `type`")
 	flag.BoolVar(&ctxt.linkShared, "linkshared", false, "link against installed Go shared libraries")

src/cmd/link/internal/ld/symtab.go

@@ -259,7 +259,7 @@ func putplan9sym(ctxt *Link, ldr *loader.Loader, s loader.Sym, char SymbolType)
 	}
 	l := 4
 	addr := ldr.SymValue(s)
-	if ctxt.IsAMD64() && !Flag8 {
+	if ctxt.IsAMD64() && !flag8 {
 		ctxt.Out.Write32b(uint32(addr >> 32))
 		l = 8
 	}