cmd/nm: fix TestGoExec on Plan 9

CL 115975 changed TestGoExec to check symbol types.
However, this test is failing on Plan 9, because
there is no read-only data segment symbol on Plan 9.

This change fixes TestGoExec to replace the check
of read-only data segment symbol (R) by data segment
symbol (D) on Plan 9.

Fixes #25820.

Change-Id: I7164cd9056fa1dfcd1dc1b0f87653290c14c85fa
Reviewed-on: https://go-review.googlesource.com/118035
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/nm/nm_test.go

@@ -157,6 +157,10 @@ func testGoExec(t *testing.T, iscgo, isexternallinker bool) {
 			t.Errorf("duplicate name of %q is found", name)
 		}
 		if stype, found := runtimeSyms[name]; found {
+			if runtime.GOOS == "plan9" && stype == "R" {
+				// no read-only data segment symbol on Plan 9
+				stype = "D"
+			}
 			if want, have := stype, strings.ToUpper(f[1]); have != want {
 				t.Errorf("want %s type for %s symbol, but have %s", want, name, have)
 			}