Add a file that proves the existence of unbundled-apache.

The build system can use this as a test for whether we
should add a dependency to the library by hand.

bug: 18027885
Change-Id: I89eb870ed47928fdd815393f8fe6f64b2a69922e
diff --git a/unbundled-apache b/unbundled-apache
new file mode 100644
index 0000000..c301258
--- /dev/null
+++ b/unbundled-apache
@@ -0,0 +1,4 @@
+The existence of this file in external/apache-http implies
+that the version of the library here is unbundled. The build system
+can test for its existence to decide whether or not to add a
+dependency to this library.