Move libctstiagent to test exports since it's for testing only.

Test: art/build/build-art-module.sh --skip-apex
      packages/modules/ArtPrebuilts/update-art-module-prebuilts.py \
        --local-dist out/dist --skip-apex
      m nothing
Bug: 172480615
Change-Id: I815d58e06cae2b4f82f9e6175cdd7098fcce3b2f
diff --git a/build/sdk/Android.bp b/build/sdk/Android.bp
index a0f11ed..79abbc1 100644
--- a/build/sdk/Android.bp
+++ b/build/sdk/Android.bp
@@ -140,9 +140,6 @@
                 "libnativehelper_compat_libc++",
                 "libnativeloader_lazy",
             ],
-            native_static_libs: [
-                "libctstiagent",
-            ],
         },
 
         linux_bionic: {
@@ -262,4 +259,7 @@
     native_shared_libs: [
         "libjavacoretests",
     ],
+    native_static_libs: [
+        "libctstiagent",
+    ],
 }