Move libdexfile out of runtime

Move the files out of runtime, leaving unfortunate dependences still
there on runtime/base (for the moment).  Also separates the build logic
into two Android.bp files.

Bug: 22322814
Test: make -j 50 test-art-host
Change-Id: Ib0a1cda833b29ecfa4c8c50f23fab89ba666f491
diff --git a/Android.bp b/Android.bp
index 4bcceff..ad42d3f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -36,6 +36,7 @@
     "dt_fd_forward",
     "dt_fd_forward/export",
     "imgdiag",
+    "libdexfile",
     "oatdump",
     "openjdkjvm",
     "openjdkjvmti",