cmd/internal/obj: remove unused GOROOT-related fields

Change-Id: I6634f70d6bd1a4eced47eda69a2d9b207d222a1b
Reviewed-on: https://go-review.googlesource.com/29470
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/cmd/internal/obj/link.go

@@ -673,8 +673,6 @@ type Link struct {
 	Flag_optimize bool
 	Bso           *bufio.Writer
 	Pathname      string
-	Goroot        string
-	Goroot_final  string
 	Hash          map[SymVer]*LSym
 	LineHist      LineHist
 	Imports       []string

src/cmd/internal/obj/obj.go

@@ -31,7 +31,6 @@ type LineHist struct {
 	TrimPathPrefix    string      // remove leading TrimPath from recorded file names
 	PrintFilenameOnly bool        // ignore path when pretty-printing a line; internal use only
 	GOROOT            string      // current GOROOT
-	GOROOT_FINAL      string      // target GOROOT
 }
 
 // A LineStack is an entry in the recorded line history.

src/cmd/internal/obj/sym.go

@@ -42,8 +42,6 @@ func Linknew(arch *LinkArch) *Link {
 	ctxt.Hash = make(map[SymVer]*LSym)
 	ctxt.Arch = arch
 	ctxt.Version = HistVersion
-	ctxt.Goroot = GOROOT
-	ctxt.Goroot_final = os.Getenv("GOROOT_FINAL")
 
 	var buf string
 	buf, _ = os.Getwd()
@@ -54,7 +52,6 @@ func Linknew(arch *LinkArch) *Link {
 	ctxt.Pathname = buf
 
 	ctxt.LineHist.GOROOT = GOROOT
-	ctxt.LineHist.GOROOT_FINAL = ctxt.Goroot_final
 	ctxt.LineHist.Dir = ctxt.Pathname
 
 	ctxt.Headtype.Set(GOOS)