cmd/compile: remove -dolinkobj flag

This used to be used by cmd/vet and some assembly generation tests, but
those were removed in CL 37691 and CL 107336. No point in keeping an
unneeded flag around.

Fixes #28220.

Change-Id: I59f8546954ab36ea61ceba81c10d6e16d74b966a
Reviewed-on: https://go-review.googlesource.com/c/142677
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/go.go

@@ -92,7 +92,6 @@ var pragcgobuf [][]string
 
 var outfile string
 var linkobj string
-var dolinkobj bool
 
 // nerrors is the number of compiler errors reported
 // since the last call to saveerrors.

src/cmd/compile/internal/gc/main.go

@@ -218,7 +218,6 @@ func Main(archInit func(*Arch)) {
 	if sys.MSanSupported(objabi.GOOS, objabi.GOARCH) {
 		flag.BoolVar(&flag_msan, "msan", false, "build code compatible with C/C++ memory sanitizer")
 	}
-	flag.BoolVar(&dolinkobj, "dolinkobj", true, "generate linker-specific objects; if false, some invalid code may compile")
 	flag.BoolVar(&nolocalimports, "nolocalimports", false, "reject local (relative) imports")
 	flag.StringVar(&outfile, "o", "", "write output to `file`")
 	flag.StringVar(&myimportpath, "p", "", "set expected package import `path`")
@@ -606,7 +605,6 @@ func Main(archInit func(*Arch)) {
 	timings.Start("fe", "escapes")
 	escapes(xtop)
 
-	if dolinkobj {
 	// Collect information for go:nowritebarrierrec
 	// checking. This must happen before transformclosure.
 	// We'll do the final check after write barriers are
@@ -671,7 +669,6 @@ func Main(archInit func(*Arch)) {
 		Ctxt.DwFixups = nil
 		genDwarfInline = 0
 	}
-	}
 
 	// Phase 9: Check external declarations.
 	timings.Start("be", "externaldcls")

src/cmd/compile/internal/gc/obj.go

@@ -43,10 +43,6 @@ const (
 )
 
 func dumpobj() {
-	if !dolinkobj {
-		dumpobj1(outfile, modeCompilerObj)
-		return
-	}
 	if linkobj == "" {
 		dumpobj1(outfile, modeCompilerObj|modeLinkerObj)
 		return