cmd/go: skip TestScript/mod_patterns on nocgo builders

Updates #26906.

Change-Id: I61b08180aefe9cfc109a1009ca251ee6970eb2df
Reviewed-on: https://go-review.googlesource.com/128879
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go/testdata/script/mod_patterns.txt

+# Broken on nocgo builders: https://golang.org/issue/26906
+[!cgo] skip
+
 env GO111MODULE=on
 
 cd m