Skip microdroid_crash_kernel for riscv64

Fix building aosp_riscv64 by removing the dependency from microdroid
to microdroid_crashdump_kernel, which doesn't have a riscv64 prebuilt
yet.

Bug: 273792258
Test: lunch aosp_riscv64-eng && m
Change-Id: I520df742cea34189332da008684380105ec51f96
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 9c9be6c..de06d01 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -110,13 +110,26 @@
                 "authfs",
                 "authfs_service",
                 "encryptedstore",
-                "microdroid_crashdump_kernel",
                 "microdroid_kexec",
                 "microdroid_manager",
                 "zipfuse",
             ],
         },
     },
+    arch: {
+        // b/273792258: These could be in multilib.lib64 except that
+        // microdroid_crashdump_kernel doesn't exist for riscv64 yet
+        arm64: {
+            deps: [
+                "microdroid_crashdump_kernel",
+            ],
+        },
+        x86_64: {
+            deps: [
+                "microdroid_crashdump_kernel",
+            ],
+        },
+    },
     linker_config_src: "linker.config.json",
     base_dir: "system",
     dirs: microdroid_rootdirs,