Reenable libc++ host dynamic lib

prebuilts/sdk/tools/.../libc++.so no longer gets installed, so it
doesn't conflict with this definition.

Change-Id: I832aca3898c47ad97b29222c2728cfe2173d56df
diff --git a/Android.bp b/Android.bp
index 81670e3..41de673 100644
--- a/Android.bp
+++ b/Android.bp
@@ -80,12 +80,6 @@
         },
         host: {
             ldflags: ["-nodefaultlibs"],
-            // Don't build for unbundled branches
-            product_variables: {
-                unbundled_build: {
-                    enabled: false,
-                },
-            },
         },
         darwin: {
             unexported_symbols_list: "lib/libc++unexp.exp",