cmd/internal/ld: change string vars into constants where possible

Change-Id: Ib3d7928bbdba9358e68a326a53effe483ec208ea
Reviewed-on: https://go-review.googlesource.com/7061
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/internal/ld/ar.go

@@ -36,9 +36,10 @@ const (
 	SAR_HDR = 16 + 44
 )
 
-var ARMAG string = "!<arch>\n"
-
-var ARFMAG string = "`\n"
+const (
+	ARMAG  = "!<arch>\n"
+	ARFMAG = "`\n"
+)
 
 type ArHdr struct {
 	name string

src/cmd/internal/ld/lib.go

@@ -258,9 +258,10 @@ const (
 	AssumeGoldLinker = 0
 )
 
-var symname string = "__.GOSYMDEF"
-
-var pkgname string = "__.PKGDEF"
+const (
+	symname = "__.GOSYMDEF"
+	pkgname = "__.PKGDEF"
+)
 
 var cout *os.File
 

src/cmd/internal/ld/objfile.go

@@ -12,9 +12,10 @@ import (
 	"strings"
 )
 
-var startmagic string = "\x00\x00go13ld"
-
-var endmagic string = "\xff\xffgo13ld"
+const (
+	startmagic = "\x00\x00go13ld"
+	endmagic   = "\xff\xffgo13ld"
+)
 
 func ldobjfile(ctxt *Link, f *Biobuf, pkg string, length int64, pn string) {
 	start := Boffset(f)

src/cmd/internal/ld/pobj.go

@@ -40,7 +40,7 @@ import (
 
 // Reading object files.
 
-var noname string = "<none>"
+const noname = "<none>"
 
 var paramspace string = "FP"