cmd/link: skip TestDWARF when cgo is disabled

While we're here, fix a Skip/Skipf error I noticed.

Fixes #19796.

Change-Id: I59b1f5b5ea727fc314acfee8445b3de0b5af1e46
Reviewed-on: https://go-review.googlesource.com/38992
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/link/dwarf_test.go b/src/cmd/link/dwarf_test.go
index 4c7e2e4..f88aecc 100644
--- a/src/cmd/link/dwarf_test.go
+++ b/src/cmd/link/dwarf_test.go
@@ -20,6 +20,7 @@
 )
 
 func TestDWARF(t *testing.T) {
+	testenv.MustHaveCGO(t)
 	testenv.MustHaveGoBuild(t)
 
 	if runtime.GOOS == "plan9" {
diff --git a/src/cmd/link/linkbig_test.go b/src/cmd/link/linkbig_test.go
index d793c2f..960d89f 100644
--- a/src/cmd/link/linkbig_test.go
+++ b/src/cmd/link/linkbig_test.go
@@ -21,7 +21,7 @@
 
 func TestLargeText(t *testing.T) {
 	if testing.Short() || (obj.GOARCH != "ppc64le" && obj.GOARCH != "ppc64" && obj.GOARCH != "arm") {
-		t.Skip("Skipping large text section test in short mode or on %s", obj.GOARCH)
+		t.Skipf("Skipping large text section test in short mode or on %s", obj.GOARCH)
 	}
 	testenv.MustHaveGoBuild(t)