FDroid: Declare optional libraries w/o risk of breaking pre-19.1 builds
diff --git a/FDroid/Android.mk b/FDroid/Android.mk
index 9db520a..3f0430a 100644
--- a/FDroid/Android.mk
+++ b/FDroid/Android.mk
@@ -5,5 +5,9 @@
LOCAL_MODULE_CLASS := APPS
LOCAL_MODULE_SUFFIX := $(COMMON_ANDROID_PACKAGE_SUFFIX)
LOCAL_CERTIFICATE := PRESIGNED
+# these lines may break builds before 19.1 so make them conditional
+ifneq ($(call math_gt_or_eq, $(PLATFORM_SDK_VERSION), 31),)
+LOCAL_OPTIONAL_USES_LIBRARIES := androidx.window.extensions androidx.window.sidecar
+endif
LOCAL_PRODUCT_MODULE := true
include $(BUILD_PREBUILT)