Add creachadair-stringset module

Bug: 137798757
Test: build on build-tools branch
Change-Id: I42e82ffd2c753718ac32d26c40af7093ff2a67cb
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..de33292
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,8 @@
+// Needed by Go extractor.
+bootstrap_go_package {
+    name: "creachadair-stringset",
+    pkgPath: "bitbucket.org/creachadair/stringset",
+    srcs: [
+        "stringset.go",
+    ],
+}