Add unit tests for libziparchive.

- Add a build rule for host tests
- Add basic tests for Find / Iterate and Extract
  for both deflated & stored entries.
- Fix an off by one error that the test uncovered.

Change-Id: If72009b1ea9791d5a265829f05c32ffe1c2752c4
diff --git a/libziparchive/zip_archive.cc b/libziparchive/zip_archive.cc
index b63ac79..43312b4 100644
--- a/libziparchive/zip_archive.cc
+++ b/libziparchive/zip_archive.cc
@@ -243,7 +243,7 @@
 
   uint32_t count = 0;
   uint64_t crc = 0;
-  while (count <= length) {
+  while (count < length) {
     uint32_t remaining = length - count;
 
     // Safe conversion because kBufSize is narrow enough for a 32 bit signed