Set apex_available property

The marked library(ies) were available to the APEXes via the hand-written
whitelist in build/soong/apex/apex.go. Trying to remove the whitelist
by adding apex_available property to the Android.bp of the libraries.

Bug: 150999716
Test: m
Change-Id: Iaf7967c1426c1e14edf7f45dc8b4eef452bbc7f9
diff --git a/Android.bp b/Android.bp
index b852276..5779397 100644
--- a/Android.bp
+++ b/Android.bp
@@ -47,6 +47,10 @@
     defaults: ["libc++abi_defaults"],
     host_supported: false,
     srcs: ["src/cxa_demangle.cpp"],
+    apex_available: [
+        "//apex_available:platform",
+        "//apex_available:anyapex",
+    ],
 }
 
 cc_library_static {
@@ -130,4 +134,8 @@
             ],
         }
     },
+    apex_available: [
+        "//apex_available:platform",
+        "//apex_available:anyapex",
+    ],
 }