Keep symbol for riscv64

Test: lunch aosp_riscv64-userdebug && ./art/tools/buildbot-build.sh --target
Change-Id: I373db6afdc5d1821abfcf4c878489b2c45251de9
diff --git a/runtime/Android.bp b/runtime/Android.bp
index beccf27..c731345 100644
--- a/runtime/Android.bp
+++ b/runtime/Android.bp
@@ -59,6 +59,11 @@
                 keep_symbols: true,
             },
         },
+        android_riscv64: {
+            strip: {
+                keep_symbols: true,
+            },
+        },
         android_x86: {
             strip: {
                 keep_symbols: true,