Find curl_ca_bundle script is used by linux only. Move it out of
gyp and make sure it runs only in linux.
Also make zlib deps generic for all systems, not for linux only.
This is the first step of getting edash_packager builds on Windows
and Mac.
Change-Id: I82d3e5872fd0dd6f57127890bc062490332a1b69
Fix "Problem with the SSL CA cert" issue @
https://github.com/google/edash-packager/issues/6. On Ubuntu, CURL_CA_BUNDLE
is located at "/etc/ssl/certs/ca-certificates.crt" while on CentOs, it is
located at "/etc/ssl/certs/ca-bundle.crt".
With this change, GYP scans the common appearing locations for SSL CA cert.
Change-Id: I838bae3954ec51f1430c900d1e82596d45a4db84
KongQun Yang