errors/fmt: disable failing TestPanics test on builders

Now that golang/go#32528 has been resolved and inner modules
are being tested too, disable this failing test until it can
be fixed. We don't want to distract people trying to do other
work in x/exp with trybot failures.

Updates golang/go#30622

Change-Id: Ia6f9c2b64100c7a9056a013453caf6e6c76177ad
Reviewed-on: https://go-review.googlesource.com/c/exp/+/196034
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/errors/fmt/fmt_test.go b/errors/fmt/fmt_test.go
index 37ace24..17d7fce 100644
--- a/errors/fmt/fmt_test.go
+++ b/errors/fmt/fmt_test.go
@@ -9,6 +9,7 @@
 	. "fmt"
 	"io"
 	"math"
+	"os"
 	"reflect"
 	"runtime"
 	"strings"
@@ -1678,6 +1679,9 @@
 }
 
 func TestPanics(t *testing.T) {
+	if os.Getenv("GO_BUILDER_NAME") != "" {
+		t.Skipf("skipping broken test on builders; see https://golang.org/issue/30622")
+	}
 	for i, tt := range panictests {
 		s := Sprintf(tt.fmt, tt.in)
 		if s != tt.out {