Change BUILD.gn so that minizip can be built with NaCL toolchain.

MiniZip will be used by Zip Archiver, which is built with NaCL toolchain. MiniZip will be moved to src/third_party/ in the future, but it will take time, so now we just use minizip here.

Review-Url: https://codereview.chromium.org/2799213002
Cr-Commit-Position: refs/heads/master@{#462779}

third_party/zlib/BUILD.gn

@@ -117,7 +117,7 @@ static_library("minizip") {
       "contrib/minizip/iowin32.h",
     ]
   }
-  if (is_mac || is_ios || is_android) {
+  if (is_mac || is_ios || is_android || is_nacl) {
     # Mac, Android and the BSDs don't have fopen64, ftello64, or fseeko64. We
     # use fopen, ftell, and fseek instead on these systems.
     defines = [ "USE_FILE32API" ]