vm: DRY *Config structs w.r.t. aflags using cfg_if

Use cfg_if to further reduce the scope of the code difference between
different flag configurations, removing the risk of differing APIs and
removing the duplication/boilerplate code, which increases the chance of
subtle differences going unnoticed.

Note: no functional change intended.

Test: banchan com.android.virt aosp_arm64 && m apps_only dist
Change-Id: Idf3fc84f78fea3c2168aee346aa50e8114bd5691
diff --git a/android/vm/Android.bp b/android/vm/Android.bp
index c1d9b6b..ba8b416 100644
--- a/android/vm/Android.bp
+++ b/android/vm/Android.bp
@@ -16,6 +16,7 @@
         "libbinder_rs",
         "libclap",
         "libenv_logger",
+        "libcfg_if",
         "libglob",
         "libhypervisor_props",
         "liblibc",