cmd/link: skip TestFlagW on platforms without DWARF symbol table

As with other DWARF tests, don't run TestFlagW on platforms
where executables don't have a DWARF symbol table.

Fixes golang#75585

Change-Id: I81014bf59b15e30ac1b2a7d24a52f9647db46c26
Reviewed-on: https://go-review.googlesource.com/c/go/+/706418
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Carlos Amedee <[email protected]>

Author: millerresearch

src/cmd/link/dwarf_test.go

@@ -364,6 +364,10 @@ func TestFlagW(t *testing.T) {
 	if runtime.GOOS == "aix" {
 		t.Skip("internal/xcoff cannot parse file without symbol table")
 	}
+	if !platform.ExecutableHasDWARF(runtime.GOOS, runtime.GOARCH) {
+		t.Skipf("skipping on %s/%s: no DWARF symbol table in executables", runtime.GOOS, runtime.GOARCH)
+	}
+
 	t.Parallel()
 
 	tmpdir := t.TempDir()