Pin TARGET_PRODUCT to aosp_arm in integration tests

aosp/3019827 does not handle the case where integration_tests might be
run from an unlunched-terminal. In this scenario, the ninja file will be
generated at out/soong/build.ninja.

To support running integration tests with/without lunch as well for
consistency of tests across different setups (users/CI etc.), pin the
TARGET_PRODUCT to a default value (aosp_arm for now)

Test: build/soong/tests/run_integration_tests.sh without running lunch
Change-Id: I1197923867643986ed3736cfc284632aa82dca13
diff --git a/tests/lib.sh b/tests/lib.sh
index e0b319e..4c320d0 100644
--- a/tests/lib.sh
+++ b/tests/lib.sh
@@ -140,7 +140,7 @@
 
 # shellcheck disable=SC2120
 function run_soong {
-  USE_RBE=false build/soong/soong_ui.bash --make-mode --skip-ninja --skip-config --soong-only --skip-soong-tests "$@"
+  USE_RBE=false TARGET_PRODUCT=aosp_arm TARGET_RELEASE=trunk_staging TARGET_BUILD_VARIANT=userdebug build/soong/soong_ui.bash --make-mode --skip-ninja --skip-config --soong-only --skip-soong-tests "$@"
 }
 
 function create_mock_bazel {