Enable shared library for libfdt

The dtc, fdtget and now crosvm.experimental host binaries can use
libfdt. Make it a shared library instead of linking it statically into
all of these tools.

Change-Id: Ifefaaf3397ee6a1cd579bc140d03e69846e67745
diff --git a/Android.bp b/Android.bp
index 712bc4d..1863a43 100644
--- a/Android.bp
+++ b/Android.bp
@@ -10,7 +10,7 @@
         "-DNO_YAML"
     ],
 
-    static_libs: ["libfdt"],
+    shared_libs: ["libfdt"],
 
     stl: "none",
     dist: {