Compile jni_headers with minimum sdk required by its dependees

Bug: 134379140
Test: m checkbuild
Change-Id: I8f7c378cf3f277e6bc6ef90ab84c71080b20a406
diff --git a/Android.bp b/Android.bp
index 51d9698..bdca899 100644
--- a/Android.bp
+++ b/Android.bp
@@ -22,6 +22,8 @@
             enabled: true,
         },
     },
+    // The minimum sdk version required by users of this module.
+    sdk_version: "minimum",
 }
 
 cc_library_headers {