cmd/govulncheck: add missing test data

Change-Id: Ic40571f3e96516a996b06472f6ee6a71f77b1d3a
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/630255
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Zvonimir Pavlinovic <zpavlinovic@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
diff --git a/cmd/govulncheck/testdata/common/modules/novuln/go.mod b/cmd/govulncheck/testdata/common/modules/novuln/go.mod
new file mode 100644
index 0000000..87604d3
--- /dev/null
+++ b/cmd/govulncheck/testdata/common/modules/novuln/go.mod
@@ -0,0 +1,3 @@
+module golang.org/novuln
+
+go 1.23
diff --git a/cmd/govulncheck/testdata/common/modules/novuln/main.go b/cmd/govulncheck/testdata/common/modules/novuln/main.go
new file mode 100644
index 0000000..da29a2c
--- /dev/null
+++ b/cmd/govulncheck/testdata/common/modules/novuln/main.go
@@ -0,0 +1,4 @@
+package main
+
+func main() {
+}