Enable -Werror on zipalign

And fix the last warning to enable this flag.

Bug: 27695718
Change-Id: I70eb9c87530a9b982fbe83abea706908f0ce0356
diff --git a/tools/zipalign/ZipEntry.cpp b/tools/zipalign/ZipEntry.cpp
index a13b8d1..1031dbe 100644
--- a/tools/zipalign/ZipEntry.cpp
+++ b/tools/zipalign/ZipEntry.cpp
@@ -142,7 +142,7 @@
  *
  * Initializes the CDE and the LFH.
  */
-status_t ZipEntry::initFromExternal(const ZipFile* pZipFile,
+status_t ZipEntry::initFromExternal(const ZipFile*,
     const ZipEntry* pEntry)
 {
     /*
@@ -694,4 +694,3 @@
     if (mFileComment != NULL)
         ALOGD("  comment: '%s'\n", mFileComment);
 }
-