Build the host tarball by default

BUG: 124892917
Test: Local build
Change-Id: I9204d52ce2040c7f9c74ce5478e9664951e04533
(cherry picked from commit 77edb4b1cde6f07b675caf3f35d61326cbe2c221)
diff --git a/host_package.mk b/host_package.mk
index a3f482e..9280b9a 100644
--- a/host_package.mk
+++ b/host_package.mk
@@ -13,6 +13,9 @@
 $(cvd_host_package_tar): PRIVATE_TAR_FORMAT := --format=gnu
 endif
 
+# Build this by default when a developer types make
+droidcore: $(cvd_host_package_tar)
+
 # Build and store them on the build server.
 $(call dist-for-goals, dist_files, $(cvd_host_package_tar))