Fix the ndk build

multiple rules generate
out/soong/target/product/ndk/system/etc/microdroid_crashdump_kernel [-w
dupbuild=err]

Fixing above error by marking the module non-installable.

Bug: N/A
Test: build/soong/scripts/build-ndk-prebuilts.sh
Change-Id: Ia3496ca299fe2616a519aeb451a1bcc21db89c3a
diff --git a/microdroid/kdump/kernel/Android.bp b/microdroid/kdump/kernel/Android.bp
index 093e7c7..0705875 100644
--- a/microdroid/kdump/kernel/Android.bp
+++ b/microdroid/kdump/kernel/Android.bp
@@ -21,4 +21,5 @@
             src: "x86_64/kernel-5.15",
         },
     },
+    installable: false,
 }