Set min_sdk_version for the test payload

We now have GTS tests that run on previous Android releases. Because we
didn't set the min_sdk_version of the native library, loading the
library in Microdroid failed with:
'cannot locate symbol "AVmPayload_readRollbackProtectedSecret"'.

Setting min_sdk_version makes APIs that were added after the
min_sdk_version use weak linking, so loading the library will succeed.

This patch alone is not enough to fix the GTS test failures, since
loading still fails with a different error which I'm still looking into:
'dlopen failed: cannot locate symbol "AIBinder_Class_setTransactionCodeToFunctionNameMap'

Bug: 389781453
Bug: 388702766
Test: atest MicrodroidTestApp.GTS
Change-Id: If14d82b92484bfe9d206b8d86d5ea07fad9ecfe6
diff --git a/tests/testapk/Android.bp b/tests/testapk/Android.bp
index d0e045b..99300e2 100644
--- a/tests/testapk/Android.bp
+++ b/tests/testapk/Android.bp
@@ -173,6 +173,8 @@
         "liblog",
         "libprotobuf-cpp-lite-ndk",
     ],
+    // We've added support for updatable payloads in Android U.
+    min_sdk_version: "UpsideDownCake",
 }
 
 cc_library_shared {
diff --git a/tests/testapk/src/native/testbinary.cpp b/tests/testapk/src/native/testbinary.cpp
index 06c7e9d..2ab73a4 100644
--- a/tests/testapk/src/native/testbinary.cpp
+++ b/tests/testapk/src/native/testbinary.cpp
@@ -348,25 +348,40 @@
         }
 
         ScopedAStatus insecurelyReadPayloadRpData(std::array<uint8_t, 32>* out) override {
-            int32_t ret = AVmPayload_readRollbackProtectedSecret(out->data(), 32);
-            if (ret != 32) {
-                return ScopedAStatus::fromServiceSpecificError(ret);
+            if (__builtin_available(android 36, *)) {
+                int32_t ret = AVmPayload_readRollbackProtectedSecret(out->data(), 32);
+                if (ret != 32) {
+                    return ScopedAStatus::fromServiceSpecificError(ret);
+                }
+                return ScopedAStatus::ok();
+            } else {
+                return ScopedAStatus::fromExceptionCodeWithMessage(EX_SERVICE_SPECIFIC,
+                                                                   "not available before SDK 36");
             }
-            return ScopedAStatus::ok();
         }
 
         ScopedAStatus insecurelyWritePayloadRpData(
                 const std::array<uint8_t, 32>& inputData) override {
-            int32_t ret = AVmPayload_writeRollbackProtectedSecret(inputData.data(), 32);
-            if (ret != 32) {
-                return ScopedAStatus::fromServiceSpecificError(ret);
+            if (__builtin_available(android 36, *)) {
+                int32_t ret = AVmPayload_writeRollbackProtectedSecret(inputData.data(), 32);
+                if (ret != 32) {
+                    return ScopedAStatus::fromServiceSpecificError(ret);
+                }
+                return ScopedAStatus::ok();
+            } else {
+                return ScopedAStatus::fromExceptionCodeWithMessage(EX_SERVICE_SPECIFIC,
+                                                                   "not available before SDK 36");
             }
-            return ScopedAStatus::ok();
         }
 
         ScopedAStatus isNewInstance(bool* is_new_instance_out) override {
-            *is_new_instance_out = AVmPayload_isNewInstance();
-            return ScopedAStatus::ok();
+            if (__builtin_available(android 36, *)) {
+                *is_new_instance_out = AVmPayload_isNewInstance();
+                return ScopedAStatus::ok();
+            } else {
+                return ScopedAStatus::fromExceptionCodeWithMessage(EX_SERVICE_SPECIFIC,
+                                                                   "not available before SDK 36");
+            }
         }
 
         ScopedAStatus quit() override { exit(0); }