This patch:
- specializes "linux" scripts into "Ubuntu 18.04" scripts
- renames all future linux blobs on CDN:
* `firefox-linux.zip => firefox-ubuntu-18.04.zip`
* `minibrowser-gtk.zip => minibrowser-gtk-ubuntu-18.04.zip`
* `minibrowser-wpe.zip => minibrowser-wpe-ubuntu-18.04.zip`
* `minibrowser-gtk-wpe.zip => minibrowser-gtk-wpe-ubuntu-18.04.zip`
- updates downloader to deal with the new names
References #2745
This patch establishes the following convention:
- scripts `checkout_build_archive_upload.sh` and `upload.sh` now accept
build flavor instead of browser name. Build flavor fully defines the
build produced / uploaded.
- scripts under `//browser_patches/webkit` and
`//browser_patches/firefox` produce build that is specific to the host
system.