Skip the cache size check on host

When running the update simulation, we choose to skip the cache size
check for now due to the lack of "/cache" on host. And in later cls we
can implement a cache size estimator to make the check more constrained.

Also build the host version of support libraries.

Test: unit test pass
Change-Id: I3ed93c857fd02f7b62f5baba9130f75c3236e717

applypatch/freecache.cpp

@@ -111,6 +111,12 @@ static std::set<std::string> FindExpendableFiles() {
 }
 
 int MakeFreeSpaceOnCache(size_t bytes_needed) {
+#ifndef __ANDROID__
+  // TODO (xunchang) implement a heuristic cache size check during host simulation.
+  printf("Skip making (%zu) bytes free space on cache; program is running on host\n", bytes_needed);
+  return 0;
+#endif
+
   size_t free_now = FreeSpaceForFile("/cache");
   printf("%zu bytes free on /cache (%zu needed)\n", free_now, bytes_needed);