Link libc++demangle.

The demangler is moving out of libc++abi to save on bloat.

Test: make checkbuild
Bug: http://b/138245375
Change-Id: I7402894bb326f524388c9efdf86509dad50f2018
diff --git a/libc/malloc_debug/Android.bp b/libc/malloc_debug/Android.bp
index d6b8531..2bff260 100644
--- a/libc/malloc_debug/Android.bp
+++ b/libc/malloc_debug/Android.bp
@@ -27,6 +27,12 @@
     },
     native_coverage: false,
 
+    target: {
+        android: {
+            static_libs: ["libc++demangle"],
+        },
+    },
+
     // -Wno-error=format-zero-length needed for gcc to compile.
     cflags: [
         "-Wall",