[dartfuzz] Don't try to use FFI on simriscv.

TEST=dartfuzz
Bug: https://github.com/dart-lang/sdk/issues/49472
Change-Id: Ib3dc89b969197a8d27c330dfbcd4029dbf9dd22e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/251848
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>
diff --git a/runtime/tools/dartfuzz/dartfuzz_test.dart b/runtime/tools/dartfuzz/dartfuzz_test.dart
index 6cf216e..7f77a53 100644
--- a/runtime/tools/dartfuzz/dartfuzz_test.dart
+++ b/runtime/tools/dartfuzz/dartfuzz_test.dart
@@ -343,7 +343,10 @@
   bool ffiCapable(String mode1, String mode2) =>
       mode1.startsWith('jit') &&
       mode2.startsWith('jit') &&
-      (!mode1.contains('arm') && !mode2.contains('arm'));
+      !mode1.contains('arm') &&
+      !mode2.contains('arm') &&
+      !mode1.contains('riscv') &&
+      !mode2.contains('riscv');
 
   bool nestedTypesAllowed(String mode1, String mode2) =>
       (!mode1.contains('arm') && !mode2.contains('arm'));