cmd/nm: handle cgo archive

This CL also make cmd/nm accept PE object file.

Fixes #21706

Change-Id: I4a528b7d53da1082e61523ebeba02c4c514a43a7
Reviewed-on: https://go-review.googlesource.com/64890
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/objfile/goobj.go

@@ -22,12 +22,33 @@ type goobjFile struct {
 	f     *os.File // the underlying .o or .a file
 }
 
-func openGoobj(r *os.File) (rawFile, error) {
+func openGoFile(r *os.File) (*File, error) {
 	f, err := goobj.Parse(r, `""`)
 	if err != nil {
 		return nil, err
 	}
-	return &goobjFile{goobj: f, f: r}, nil
+	rf := &goobjFile{goobj: f, f: r}
+	if len(f.Native) == 0 {
+		return &File{r, []*Entry{&Entry{raw: rf}}}, nil
+	}
+	entries := make([]*Entry, len(f.Native)+1)
+	entries[0] = &Entry{
+		raw: rf,
+	}
+L:
+	for i, nr := range f.Native {
+		for _, try := range openers {
+			if raw, err := try(nr); err == nil {
+				entries[i+1] = &Entry{
+					name: nr.Name,
+					raw:  raw,
+				}
+				continue L
+			}
+		}
+		return nil, fmt.Errorf("open %s: unrecognized archive member %s", r.Name(), nr.Name)
+	}
+	return &File{r, entries}, nil
 }
 
 func goobjName(id goobj.SymID) string {